WotLK Client Erorrs

I've had issues with some crashes occurring on my icecrown characters, while this doesn't effect the ones on frostmourne
mostly it happens when i try to leave dalaran, or flying in northrend.

To explain what exactly happens before the crash is, the UI disappears and the fps drops, and the screen stutters, and then throws me out of the game with every time displaying different errors, just emphasize again this only happens on icecrown, not on frostmourne.

I was wondering has anyone had the same experience before, and if they have been able to resolve the matter.
Thank you