OS X :: MBP - Cursor Clicking / Dragging Files Automatically?

I love my 1st generation MacBook Pro 15" very much. She's running the latest Leopard update, and everything was running smoothly up until a couple of days ago. For some reason, the computer seems to think that I'm constantly holding down the mouse button. No matter what application I'm in, the cursor starts acting up - dragging boxes and files in finder, dragging things off the dock instead of hovering over them, etc etc. This doesn't happen all the time, and I'm not sure what triggers it, but it somehow seems to happen more often later in the day. Sometimes it stops within seconds, sometimes it's a couple of minutes before it goes back to normal.

Sometimes clicking the real mouse button a couple of times or pressing escape fixes it, sometimes it doesn't. My first thought was that it was Blender causing a problem, as that's the first place the problem showed up. When I noticed the same thing occuring in Finder, after a fresh reboot, I thought maybe a hack I had recently applied was the culprit, but nothing came to mind. To be on the safe side, I tried making a hack-free account and using it for a while, but to no avail-same problem (less often, however). Now, getting desperate, I switched over to my Boot Camp partition. The problem reared its ugly head there, too - not nearly as often, however...just two or three times in my two hours there.