I have a Win XP SP3 Desktop that seems to go through periods where it will not unlock with Safeboot and must be HARD reset in order to log back in. The only option I have from our support is that they will send me another laptop.. that gets old. I have been able to make the problem go away in the past.. once by simply running a registry cleaner. Now.. its not so simple.. and I am just curious if anyone else has encountered this..
Check the SbClientLog.txt on the affected machine. If you see the error "Insufficient Memory", then reboot machine, publish decrypt/unistall policy. After the uninstall is complete, reinstall fresh. Be sure to disable hibernate, as it seems to trigger this problem. Most of the machines we had that experienced this problem had hibernate enabled and were upgraded from B4770 to 5.1.7.