[HTC One S] :
Since today, both Email.app and Gmail are crashing whenever I try to open a particular mail by tapping on it. Here's the crash report from Email.app:

android.view.InflateException: Binary XML file line #28: Error inflating class com.android.mail.browse.ConversationWebView
at android.view.LayoutInflater.createView(LayoutInflater.java:633)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:743)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:809)
at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at com.android.mail.ui.ConversationViewFragment.onCreateView(ConversationViewFragment.java:384)
at android.app.Fragment.performCreateView(Fragment.java:2053)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:894)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.app.BackStackRecord.run(BackStackRecord.java:834)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1452)
at android.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:483)
at com.android.mail.utils.FragmentStatePagerAdapter2.finishUpdate(FragmentStatePagerAdapter2.java:147)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1441)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17562)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:868)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17562)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5536)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2871)
at android.view.View.measure(View.java:17562)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5891)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5292)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:288)
at android.view.LayoutInflater.createView(LayoutInflater.java:607)
... 62 more
Caused by: android.util.AndroidRuntimeException: java.lang.RuntimeException: Invalid reflection
at android.webkit.WebViewFactory.getProvider(WebViewFactory.java:137)
at android.webkit.WebView.getFactory(WebView.java:2194)
at android.webkit.WebView.ensureProviderCreated(WebView.java:2189)
at android.webkit.WebView.setOverScrollMode(WebView.java:2248)
at android.view.View.<init>(View.java:3597)
at android.view.View.<init>(View.java:3691)
at android.view.ViewGroup.<init>(ViewGroup.java:498)
at android.widget.AbsoluteLayout.<init>(AbsoluteLayout.java:55)
at android.webkit.WebView.<init>(WebView.java:544)
at android.webkit.WebView.<init>(WebView.java:489)
at android.webkit.WebView.<init>(WebView.java:472)
at android.webkit.WebView.<init>(WebView.java:459)
at com.android.mail.browse.MailWebView.<init>(MailWebView.java:24)
at com.android.mail.browse.ConversationWebView.<init>(ConversationWebView.java:160)
... 65 more
Caused by: java.lang.RuntimeException: Invalid reflection
at com.android.webview.chromium.WebViewDelegateFactory$Api21CompatibilityDelegate.<init>(WebViewDelegateFactory.java:225)
at com.android.webview.chromium.WebViewDelegateFactory.createApi21CompatibilityDelegate(WebViewDelegateFactory.java:97)
at com.android.webview.chromium.WebViewChromiumFactoryProvider.<init>(WebViewChromiumFactoryProvider.java:105)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.webkit.WebViewFactory.getProvider(WebViewFactory.java:131)
... 78 more
Caused by: java.lang.NoSuchMethodException: callDrawGLFunction [long]
at java.lang.Class.getMethod(Class.java:664)
at java.lang.Class.getMethod(Class.java:643)
at com.android.webview.chromium.WebViewDelegateFactory$Api21CompatibilityDelegate.<init>(WebViewDelegateFactory.java:212)
... 83 more

Anyone kind enough to tell me what's going on here?

EDIT: October 12.1 Snapshot, Hboot 2.15, latest Mrak kernel, Dec 6 Opengapps pico.

EDIT #2: Have meanwhile come to believe it's Gapps rather than Rom-related.

EDIT #3: I just had a look at the system logcat after one of these crashes. The first crash-related line threre read "Failed to open relro file /data/misc/shared_relro/libwebviewchromium32.relro: No such file or directory". A Google search for this error message took me to another thread here on XDA Devs (this one), where somebody suggested to try installing Android System WebView from the playstore. Done that, and ... voilà - the issue's gone.

Still don't know how or why this has happened (and whether it's rom, or gapps, or whatever-else-related), but in case somebody has similar problems ... this might solve them.