Below decsriibes exactly the prblem I am having. The thread says "solved" but the only solution suggested was to try safe mode.
I have the same problem on my Dell Optiplex 380. I lock my computer when I'm AFK. Randomly, after a period of inactivity, I will move the mouse or hit a key to wake the display, and am prompted to press ctrl+alt+del to login. However, when I press ctrl+alt+del, the actual login prompt never shows, and instead only shows the Win7 background. If I let the computer alone after that, the ctrl+alt+del prompt might appear again. Instead of hitting ctrl+alt+del, if I click "switch user," the display is then disabled and goes to power-saving mode, while the computer is seemingly still in the same state. I thought it was a hardware issue, but am now convinced this is a Windows 7 issue. Here's why:
-Dell has replaced the motherboard and memory, thinking it is a hardware problem.
-Each time the computer freezes up, which is usually after the computer is idle for some time, I have to forcibly restart the machine.
-The event logs always show the eventID posted above (10023) before the lock-up. (The protocol host process 4892 did not respond and is being forcibly terminated {filter host process 5344}.)
-I have rebuilt the search index to no avail.
-I have disabled the windows search service to no avail.