05-13-2014 05:24 AM
This appears to be a firmware issue. I had the same issue and found the answer on a forum somewhere.
Go to Settings-system settings- Backlight. If the backlight setting is at 10 seconds this causes the lock button issue. Just select the next time level (15 seconds) or better and remember to save the setting when asked.
This resolved the issue for me. I hope it does for you.