Thanks for the replies.
No, no screen saver whatsoever. What's strange to me is the lull in between the spurts of this occurring. It's been well over 48 hours now without an occurrence, and it was like that last time.
I've swapped out the keyboard and mouse with my wife's computer and still had it occur shortly after.
I'm keeping a mental log of what programs I'm using around the time this occurs, but have yet to pinpoint anything concrete yet... except "Windows"
EDIT: Is there any way to force an event log on Windows lock? An "audit" so to speak? I know you can do some pretty crazy stuff with security protocols, but it's a bit beyond me as to where to begin.
EDIT2: Asking that last question reminded me of "local policies" and sure enough, found an obvious entry for logging locking/unlocking the workstation; however, the detail on the event is unhelpful. Was hoping for information as to who/what did the locking, but i suppose outside of silly problems like mine, that's rather redundant.