SSFIV PC suddenly playing up?

I’ve been playing SSFIV AE on PC with no hitches until very recently, now suddenly the graphics
look like they’ve become 100x worse and are slightly smaller than before.

It’s not a resolution thing, I’ve already tested them all and it still looks pretty hideous.

Any idea what could have happened?

It’s still perfectly playable but it’s not very pretty.

If you don’t think it’s an issue with Windows’ or the game’s settings, best bet is backing up your save files and reinstalling the game. Did you do anything like updating your video drivers before you noticed the problem? If you have System Restore enabled, go through the calendar and see if any restore points were made around the time the issue started.