Mouse acceleration and an editor autocompletion cost me two days

After the last OSX upgrade, my mouse cursor has become very jerky and subject to frequent freezes. After some innertube research, I think the problem is the OSX mouse acceleration, and I can limit the problem by slowing down my mouse tracking speed preferences, coupled with some care in how I move the mouse physically

I have a big LaTex document I've been working on in TeXShop, and the document suddenly stopped typesetting, giving me errors

It took me two days to find the problem: an extraneous line of code suddenly appeared halfway through the big document, and it's inappropriate for the location -- it only works in the preamble. It's legit LaTeX but I had to look it up, because I've never used it

How did it appear? The only explanation I can see is the following:

First of all, when the mouse cursor "freezes," tracking doesn't really freeze: the 'puter thinks everything is fine, so if I move the mouse when the cursor is frozen, the 'puter thinks the cursor is somewhere other than it seems to be. I can sometimes see the effect of this, but it's very hard to predict, because the mouse acceleration doesn't move the actual cursor smoothly with the physical motion of the mouse

Second, the TeXShop editor has an autocompletion function, that often (but not always) works well

So my cursor freezes; I jiggle the mouse impatiently and click it a few times before sighing, unplugging it, and replugging it. I think I've been just trying to get my cursor unfrozen. TeXShop thinks I'm telling it to autocomplete something at some distance from where the screen cursor is frozen. The screen cursor reappears somewhere in the Oort Belt, and I try to typeset the document. It fails, citing some error at the very beginning of the document where no error is evident

Bad bit somewhere? If so, I can't seem to find it anyhow

Hard driving dying? It passes all the tests

TeXShop problem? Reinstalling doesn't help

Aaargh ...

Fugg mouse acceleration