[Nexus 7 Q&A, Help & Troubleshooting] Red Devil:
Hi there ! This seems to be the problem in your case :

Sending signal. PID: 349 SIG: 9

E/AndroidRuntime( 349): *** FATAL EXCEPTION IN SYSTEM PROCESS: ActivityManager

E/AndroidRuntime( 349): java.lang.ArrayIndexOutOfBoundsException: src.length=8192 srcPos=1 dst.length=8192 dstPos=0 length=-1

E/AndroidRuntime( 349): at java.lang.System.arraycopy(Native Method)

E/AndroidRuntime( 349): at org.kxml2.io.KXmlParser.fillBuffer(KXmlParser.java:1489)

E/AndroidRuntime( 349): at org.kxml2.io.KXmlParser.skip(KXmlParser.java:1574)

E/AndroidRuntime( 349): at org.kxml2.io.KXmlParser.parseStartTag(KXmlParser.java:1049)

E/AndroidRuntime( 349): at org.kxml2.io.KXmlParser.next(KXmlParser.java:369)

E/AndroidRuntime( 349): at org.kxml2.io.KXmlParser.next(KXmlParser.java:310)

E/AndroidRuntime( 349): at com.android.server.am.UsageStatsService.readHistoryStatsFLOCK(UsageStatsService.java:376)

E/AndroidRuntime( 349): at com.android.server.am.UsageStatsService.readHistoryStatsFromFile(UsageStatsService.java:357)

E/AndroidRuntime( 349): at com.android.server.am.UsageStatsService.<init>(UsageStatsService.java:274)

E/AndroidRuntime( 349): at com.android.server.am.ActivityManagerService.<init>(ActivityManagerService.java:1534)

E/AndroidRuntime( 349): at com.android.server.am.ActivityManagerService.<init>(ActivityManagerService.java:160)

E/AndroidRuntime( 349): at com.android.server.am.ActivityManagerService$AThread.run(ActivityManagerService.java:1405)

E/AndroidRuntime( 349): Error reporting crash

E/AndroidRuntime( 349): java.lang.NullPointerException

E/AndroidRuntime( 349): at com.android.internal.os.RuntimeInit$UncaughtHandler.uncaughtException(RuntimeInit.java:76)

E/AndroidRuntime( 349): at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:693)

E/AndroidRuntime( 349): at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:690)

As you can see the lines start with E:/ which stand for error .

V stands for Verbose

I for information

D for Debug.

And some others . more about these.. I suggest you Google. Now you will ask how I found out the error ? Well if you take a closer look to the log you will notice that once the kernel is initialized ( which happens at the Google logo ) the netd framework starts booting by the kernel.

Normal boot sequence is kernel > its init.rd and init.rc then the init.d and then the framework. How I came to know all this ? Take a log of a normally booting ROM :D

If you again carefully observe the log .. You will notice log re iterates. It goes on an infinite loop. Hence the term boot'loop'.

The start of the loop is

AndroidRuntime( 369): >>>>>> AndroidRuntime START com.android.internal.os.ZygoteInit <<<<<<

D/AndroidRuntime( 369): CheckJNI is OFF

And this Is the dead / bad code

ygote ( 369): Exit zygote because system server (508) has terminated

I/ServiceManager( 118): service 'sensorservice' died

I/ServiceManager( 118): service 'entropy' died

I/ServiceManager( 118): service 'power' died

That's roughly how you read a logcat.

And about your problem. I suggest a clean wipe and reflash the ROM. Its always better to keep backing up your data from time to time. I also ensure I wipe clean even during flashing nightlies .