Saints Row The Third frame reate drop.

[TUN3R]

Normally I'd be able to run Saints Row The Third perfectly (45 FPS, even 50 occasionally) with everything set to Ultra. But since yesterday, for some reason, it wouldn't run well anymore. It runs at about 5 FPS with everything set to Ultra and only gets a decent 30 FPS if everything is set to medium and low.

I tried reinstalling / updating my drivers, defragmentation, closing background programs etc (stuff I do weekly anyways). I haven't tried reinstalling the game but TBH even if it worked I wouldn't call it a solution, since I'd have to do it every time the game does this. I also don't have any mods or stuff like that, anti-virus software or programs that can slow down the game, all my other games run perfectly (or at least, as well as they always did), my HDD has plenty of space left and my GPU isn't overheating.

Hopefully I've covered all the stupid routine questions people tend to ask. PC specs:

Intel Core i5-661 3.33 GHz
8GB DDR3 RAM
GeForce GTX 550 Ti 1GB
Windows 7 Ultimate 64bit