This is very annoying: somehow my Num Lock gets turned off numerous times per day. I switch programs all the time (usually using Alt+Tab) and lock the screen when I leave my desk. Some days it happens very frequently and others very rarely. I don't generally notice right away (the light on the keyboard is out of my normal line of sight), and perhaps for this reason I have not been able to determine the pattern.
Dell Optiplex 980, Windows 7 Professional (64-bit), Office 2010 Home & Business
Web searches turn up lots of references to the start-up state of the Num Lock key, but those don't seem relevant for me.
Any thoughts? Maybe there's a little background program I can run that will ring a bell when the NumLock state changes so I have a chance of spotting a pattern.