google fails me. But firefox fails me first

I'm getting incorrect pixels on evey page and also in the menubars of firefox. It starts as a few white dots in the colored areas and colored dots in the white areas. As I stay with a page or scroll down it the speckles accumulate rapidly so that the page is illegible in a few moments. Reloading returns the page to a state of merely annoyingness. Then the process continues. I can read a page by constantly reloading it. I can ruin it scrolling or backspacing.

I tried to google "snow in browser," "pixelated browser," "speckles in browser," all of those terms with firefox instead of browser, "firefox display problems" and issues, and nothing gets me any useable answers. Apparently a month ago I could have gotten a "snow in broswer" effect but it looked different, according to the screenshot which I examined closely, reloading several times to make sure since the image, like everything else online, rapidly became illegible.

I have the dumbest computer problems. Anybody have any idea about this one? The problem does not appear on the other programs I use (none of which is also a browser, so I just don't know about that question. And I don't want to install something else just for experimental reasons).

edit: it appears to be a video problem, possibly caused by an older fan-made program I use for modding the Sims, my copy of which has recently become unstable.

so I guess I have to reinstall SimPe.