Selected cell is "copied" whenever I use scroll bar

[CrabApple]

To Whom It May Interest:

Thank you in advance for your time. I've been troubled recently Excel's behavior and have yet to devise a search query that finds the answer online.

Excel has started acting strangely recently with regard to copying cells. Anytime I touch the scroll bar (or change tabs on the ribbon), it will copy the cell last selected (so the lines around it start moving, if you know what I mean). I don't know why, as I haven't fooled with any settings. I have confirmed that it is not me accidentally holding down on my touch pad (I use a red keyboard nub to navigate the UI). I have gotten the same behavior when I use JUST the touch pad and different buttons. I have new workbooks and checked old ones; it does this in all of them.

It's irritating the heck out of me--I actually uninstalled and reinstalled Excel to see if it would stop, and it didn't. Has anybody experienced this? Does anybody have advice? It's making it very difficult to work on more than one workbook at a time, as I'm always carrying over the cell that's automatically been copied.

Sincerely,

CA