Recently I had a problem with servers booting very slowly after a restart. They seemed to not be doing anything at all, but nothing made it look like they hung. After several hours (seriously) the servers booted into Windows. The logfiles were clean, however I was unable to start / stop services. Users couldn't print and Exchange wasn't working.
Users could, however, use their files and some SQL databases.

It turned out that the APC software had "expired".
The solution is booting in safe mode, and setting the following services to "manual":
- APCPBEServer

This already fixes all problems.

Then reboot and download APC v.7 to keep your UPS's functioning properly.

Here's the link: