In the past two weeks I've seen this issue skyrocket among Win7 (even Vista!) systems. I've tried AV scans of every affected system; System Restore (when restore points are available) seems to fix the issue.
To summarize, the systems boot to a black screen with a moveable cursor. CTRL+ALT+DELETE does nothing. Same goes for Safe Mode. Virus scans of the hard drive (when the drive is mounted onto a working system) come back clean (for the most part). Malware is generally the same. I've tried many possible solutions online, but none have worked.
I have noticed that some of the Restore points show an Windows Update was done shortly before the issue happens.
So far I have had to do either a System Restore or Factory Image reset. The System Restore, however, showed problems in the registry (Windows Update failures [after restore], AV update failure, services not running, etc) which led to a Factory Image reset in the end. I was unable to resolve registry issues.
I've managed to backup client data each time with no loss, but I feel like I'm using dynamite to take out the trash. Is there something I'm missing?