So, it seems that I've run into a bit of a unique issue (at least as far as I can tell, it could just be that I'm terrible at searching x.x). After being in the game for a few seconds, my cursor will begin to toggle between attack and normal functions. If I go into any sort of menu, the issue is fixed, but when I got back to being able to walk around, it starts back up after a few seconds.

Just to clarify, this happens in both (original and unmodded) Baldur's Gate games as well as both (also original and unmodded) Icewind Dale games. And, just incase I'm not adequately describing what's happening, here's a video actually showing what's happening. https://youtu.be/hCzpzrhJ7M4

Edit: The footage is from a modded version of Baldur's Gate 2, but the issue is still there regardless of mods.

That did it, thanks. Feel kind of stupid, considering that's the classic fix for just about every issue in Windows. :-p