I suddenly got extremely slow animations on doors, containers and spell-effects. Rest of the game runs as usual, afaict. It can take 10-15sec for a door to open. Restarting game and/or computer don't help. Older saves seem to run ok at a quick glance.
You're on the PC? If so you're lucky. It's called the A-Bomb that happens to every game after a certain number of hours, but can be fixed if your on the PC
If interested, you can read more of the issue here: http://www.gamesas.com/index.php?/topic/813915-slowfrozen-doors-fire-spell-etc-animations-thread-8-of-jittering-doorseffectsobjects/page__p__11828804__fromsearch__1entry11828804