So basically, I get about 1 to 2 frames per second in the Mages Guild hall in Leyawiin. I can run the rest of the game fine on medium graphics. Is there any particular reason that this would happen?

Are there any mods you use that affect that guild hall?
Also the Leyawiin Mages Guild Hall is slightly bigger then most of the others.

Much of Leyawiin is poorly optimized, and it doesn't help that the Leyawiin hall is a big one. You might consider investing some time into tweaking/modding your game to improve performance. In short, this probably isn't a bug and it's just your system showing it's age.