Remove any random stat generated item from your guild banks (like green armor/weapon items). I'm pretty sure that they cause random WoW errors. If you ever got a WoW error by browsing the guild bank, it's because a green, random stat generated item is in than tab. So, if you manage to open a tab without errors, just remove them.
Me and some friends had lots of trouble browsing our guild bank but after i decided to remove all the crappy greens, we are all error free ever since. I even added some greens to test and see if i get an error and i did.
I think this only applies for the guild banks, your personal bank doesn't have this bug (not 100% sure though but i never had a problem)
I don't know if that's a known issue but i thought i share this for anyone who missed it.
