I'm in Windows hell at work, where I'm forced to use Windows XP Professional (5.1). In the last couple of weeks, a strange problem has been recurring.
When working with text in various applications (Word, Notepad, Lotus Notes...), a seemingly random point will get tagged as a selection endpoint. So when I click anywhere else -- either before or after -- it selects the text between that point and wherever I've clicked. The annoying thing is that I can't seem to escape from this. It will not let me reposition the cursor and move on.
Interestingly, when this problem occurs, it is not restricted to the app I'm working in. It seems to apply to all "text editing" apps. So, for example, if it's doing this in Lotus Notes and I switch over to Notepad, the problem carries over to Notepad. The only way I've found to escape is to reboot.
At first, I assumed I had accidentally hit some key sequence. But since this just started a couple of weeks ago, and is now happening with annoying regularity (and across different apps), I think it's something bigger.
"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer sscce.org
I recall having this exact same issue several months back. I think it took going to Windows Update and installing just about all of the patches, and updating the keyboard and mouse drivers to the latest versions to fix it. Unfortunately, I cannot point to a single, specific thing I did to solve it.
I'll think about the problem some more, it I recall anything else I'll post it.