Locking screen on idle does not work reliably

[ilpssun]

Since upgrading from 12.04 to 12.10, the locking of my screen on idle does not work reliably anymore. Sometimes, the screen goes black as it should but it can be reactivated without a password. Most of the time, the password is required. If I trigger the locking using the hotkey ("pause" key in my case), the locking seems to be reliable.

This is very annoying because I already entered my password into a GEdit text file without noticing and sent it out via Pidgin.

I have not yet found any pattern or regularity, so I'm sorry that I can't provide a more helpful bug report.