I had this weird experience: on doing one of the thief's guild missions, my character slowed down A LOT. I thought that was some stat damage, and I went to a chapel to heal. It didn't work. So I got both the fast save (trying to sneak past the head of Imperial city guards) and the autosave gone. My previous save was 6 hours ago... PLEASE!!!! I need some help!
Nope. The "damage" doesn't even appear on the "active effect screen. And nothing seems to cure it. I tried throwing to the ground everything I could and the effect stayed. Slow as a slug; with SPEED 76!
at first I tought that you pressed caps lock or you have too much items, but when I read little more, I realized its bug, try downloading lastest patch
If you have the game of the year addition, get the non-game of the year addition and upload your game account onto the and see if it works. If it does, then save it and go back to game of the year addition. That worked with the Cure of Vampirism quest. But if you do have the game of the year addition and you upload game stuff on non-game of the year and switch back, you lose all stuff you got from the the magical city that starts with the quest "Door to Niben Bay". I lost all my armor because of that and for some reason I found my own dead body. I couldn't search it though.
I found other people with the same problem. I tried downloading an add-on that would set the stat to normal value, all it did was bringing the speed from slug-like to tortoise-like....