Mouse hardware doing something odd..
This happens with both my mouse and my tablet-- it just started doing this randomly one day.
When I go to click something, it acts like it double clicks, and then the "second click" holds onto the area on my computer.. so for example, when I pull away, it highlights the page, or automatically scolls down on the page.. or if I'm drawing and I pull the pen away, it continues to make a line anyhow. I don't know what's up with this. I thought it was my mouse at first, but it's my tablet too-- so I guess I don't have a faulty mouse. Any clues toward why this may be happening? The mouse settings aren't changed or anything.