Glad you got it sorted out.   I think you are justified to be cautious.  Maybe the UPS software simply got corrupted, or maybe it is a bug needing a patch, updated software, certain Windows updates, or both, or perhaps it is conflicting with another program or service installed on your server.  I would certainly investigate before trying it again ... perhaps APC has a fix - or acknowledges the problem with no fix [yet].
Came in this morning and found server completely unresponsive.  Could not connect to it in any fashion.  Did a hard power off.  Upon powering back up, the post screen pops up for just a moment and then disappears.  Can see the drives in the raid array polling every now and then but absolutely nothing displaying on screen. Help?  Gary 
Poweredge 1800 server will not boot after improper shutdown