I've got these problems:

1) sometimes winlogon.exe crashes at boot-up and my whole computer shuts off once i click "no" to visual-studio-2008 just-in-time-debugger window, takes about 30 secs until my harddrives starts up again, its really scary, i am afraid it is causing hardware malfunctions in long term. this has happened dozen of time now.

2) sometimes i leave the computer alone a while, i come back and i notice ctrl+alt+del doesnt work and winlogon.exe is using 100% of one of my 4 cores.