[Nexus 6 Android Development] ebthepcguy:
Just ran logcat and got

04-12 13:19:14.307 724 6905 I LockSettingsService: Initialize SyntheticPassword for user: 0
04-12 13:19:14.346 724 6905 I LockSettingsService: Caching SP for user 0
04-12 13:19:14.347 724 724 I LockSettingsService: Removing SP from cache for user 0
04-12 13:19:14.425 246 246 I hwservicemanager: getTransport: Cannot find entry android.hardware.weaver@1.0::IWeaver/default in either framework or device manifest.
04-12 13:19:14.427 724 6905 I SyntheticPasswordManager: Device does not support weaver
04-12 13:19:14.430 544 544 D PermissionCache: checking android.permission.ACCESS_KEYGUARD_SECURE_STORAGE for uid=1000 => granted (1853 us)
04-12 13:19:14.792 519 519 D keystore: AddAuthenticationToken: timestamp = 150824, time_received = 150
04-12 13:19:14.841 519 519 I keystore: del USRPKEY_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.842 519 519 I keystore: del USRSKEY_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.842 519 519 I keystore: del USRCERT_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.842 519 519 I keystore: del CACERT_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.845 519 519 I keystore: del USRPKEY_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.845 519 519 I keystore: del USRSKEY_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.846 519 519 I keystore: del USRCERT_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.846 519 519 I keystore: del CACERT_synthetic_password_a75fcdeb26415242 1000
04-12 13:19:14.861 519 8417 D DropBoxManager: About to call service->add()
04-12 13:19:14.862 724 2771 I DropBoxManagerService: add tag=keymaster isTagEnabled=true flags=0x0
04-12 13:19:14.865 519 8417 D DropBoxManager: service->add returned No error
04-12 13:19:14.880 250 250 D vold : fscrypt_add_user_key_auth 0 serial=0 token_present=0
04-12 13:19:14.881 519 519 I keystore: Secure lockscreen for user 0 removed, deleting encrypted entries
04-12 13:19:14.943 544 544 E gatekeeperd: clear_sid: could not remove file [No such file or directory], attempting 0 write
04-12 13:19:14.944 250 250 D vold : fscrypt_fixate_newest_user_key_auth 0
04-12 13:19:14.970 724 6905 E LockSettingsStorage: Cannot read file java.io.FileNotFoundException: /data/system_de/0/spblob/a75fcdeb26415242.weaver: open failed: ENOENT (No such file or directory)
04-12 13:19:14.972 519 519 D keystore: AddAuthenticationToken: timestamp = 151177, time_received = 151
04-12 13:19:15.006 724 6905 W System.err: javax.crypto.IllegalBlockSizeException
04-12 13:19:15.007 724 6905 W System.err:	at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:519)
04-12 13:19:15.007 724 6905 W System.err:	at javax.crypto.Cipher.doFinal(Cipher.java:2055)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.SyntheticPasswordCrypto.decrypt(SyntheticPasswordCrypto.java:66)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.SyntheticPasswordCrypto.decryptBlob(SyntheticPasswordCrypto.java:144)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.SyntheticPasswordManager.decryptSPBlob(SyntheticPasswordManager.java:1137)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.SyntheticPasswordManager.unwrapSyntheticPasswordBlob(SyntheticPasswordManager.java:998)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.SyntheticPasswordManager.unwrapPasswordBasedSyntheticPassword(SyntheticPasswordManager.java:927)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.LockSettingsService.spBasedSetLockCredentialInternalLocked(LockSettingsService.java:2800)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.LockSettingsService.setLockCredentialInternal(LockSettingsService.java:1603)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.server.locksettings.LockSettingsService.setLockCredential(LockSettingsService.java:1522)
04-12 13:19:15.007 724 6905 W System.err:	at com.android.internal.widget.ILockSettings$Stub.onTransact(ILockSettings.java:503)
04-12 13:19:15.007 724 6905 W System.err:	at android.os.Binder.execTransactInternal(Binder.java:1021)
04-12 13:19:15.007 724 6905 W System.err:	at android.os.Binder.execTransact(Binder.java:994)
04-12 13:19:15.008 724 6905 W System.err: Caused by: android.security.KeyStoreException: Key user not authenticated
04-12 13:19:15.008 724 6905 W System.err:	at android.security.KeyStore.getKeyStoreException(KeyStore.java:1292)
04-12 13:19:15.008 724 6905 W System.err:	at android.security.keystore.KeyStoreCryptoOperationChunkedStreamer.update(KeyStoreCryptoOperationChunkedStreamer.java:132)
04-12 13:19:15.008 724 6905 W System.err:	at android.security.keystore.KeyStoreCryptoOperationChunkedStreamer.doFinal(KeyStoreCryptoOperationChunkedStreamer.java:217)
04-12 13:19:15.008 724 6905 W System.err:	at android.security.keystore.AndroidKeyStoreAuthenticatedAESCipherSpi$BufferAllOutputUntilDoFinalStreamer.doFinal(AndroidKeyStoreAuthenticatedAESCipherSpi.java:373)
04-12 13:19:15.008 724 6905 W System.err:	at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:506)
04-12 13:19:15.008 724 6905 W System.err:	... 12 more
04-12 13:19:15.009 724 6905 E JavaBinder: *** Uncaught remote exception! (Exceptions are not yet supported across processes.)
04-12 13:19:15.009 724 6905 E JavaBinder: java.lang.RuntimeException: Failed to decrypt blob
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.SyntheticPasswordCrypto.decryptBlob(SyntheticPasswordCrypto.java:152)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.SyntheticPasswordManager.decryptSPBlob(SyntheticPasswordManager.java:1137)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.SyntheticPasswordManager.unwrapSyntheticPasswordBlob(SyntheticPasswordManager.java:998)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.SyntheticPasswordManager.unwrapPasswordBasedSyntheticPassword(SyntheticPasswordManager.java:927)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.LockSettingsService.spBasedSetLockCredentialInternalLocked(LockSettingsService.java:2800)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.LockSettingsService.setLockCredentialInternal(LockSettingsService.java:1603)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.LockSettingsService.setLockCredential(LockSettingsService.java:1522)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.internal.widget.ILockSettings$Stub.onTransact(ILockSettings.java:503)
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.os.Binder.execTransactInternal(Binder.java:1021)
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.os.Binder.execTransact(Binder.java:994)
04-12 13:19:15.009 724 6905 E JavaBinder: Caused by: javax.crypto.IllegalBlockSizeException
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:519)
04-12 13:19:15.009 724 6905 E JavaBinder:	at javax.crypto.Cipher.doFinal(Cipher.java:2055)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.SyntheticPasswordCrypto.decrypt(SyntheticPasswordCrypto.java:66)
04-12 13:19:15.009 724 6905 E JavaBinder:	at com.android.server.locksettings.SyntheticPasswordCrypto.decryptBlob(SyntheticPasswordCrypto.java:144)
04-12 13:19:15.009 724 6905 E JavaBinder:	... 9 more
04-12 13:19:15.009 724 6905 E JavaBinder: Caused by: android.security.KeyStoreException: Key user not authenticated
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.security.KeyStore.getKeyStoreException(KeyStore.java:1292)
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.security.keystore.KeyStoreCryptoOperationChunkedStreamer.update(KeyStoreCryptoOperationChunkedStreamer.java:132)
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.security.keystore.KeyStoreCryptoOperationChunkedStreamer.doFinal(KeyStoreCryptoOperationChunkedStreamer.java:217)
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.security.keystore.AndroidKeyStoreAuthenticatedAESCipherSpi$BufferAllOutputUntilDoFinalStreamer.doFinal(AndroidKeyStoreAuthenticatedAESCipherSpi.java:373)
04-12 13:19:15.009 724 6905 E JavaBinder:	at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineDoFinal(AndroidKeyStoreCipherSpiBase.java:506)
04-12 13:19:15.009 724 6905 E JavaBinder:	... 12 more

Looks like an error with the encryption, but I'm not familiar with the way Android stores this info.