In 4 days since I installed 3.5.31 I've had to reset (as in wipe cache, wipe data) my SGS2 twice because in normal use the phone locks up, and on restarting (hard power off or battery remove) it doesn't get past the initial firmware bootloader screen - i.e. fails to even get to the usual animated Samsung logo. Just goes black screen, no progress. Restarting doesn't change it - once the lock happens, I cannot boot the phone even if I re-flash the 3.5.31 rom. The problem persists until I clear data. REALLY frustrating. Don't know what I was doing when this happened first on Saturday. But the second time (Sunday?) was while using Bacon Reader. And tonight it froze again while using Google Maps. I've left phone running on the frozen screen this time as I am sick of resetting and restoring from backup, wanted to see what happens when the battery drains rather than hard reboot. I have no idea what's causing the locks - possibly an app, possibly not - so wondering if anyone else is facing this issue.