Can't get it, but Mutliboxing isn't the reason for that, I used AHK with 5 Char's for about 25-30 levels nothing happened...

Are you running it with different Path's for your WoW? I Mean something like 3 (or whatever number you want to Box) Folders with a WoW Copy for it self? or are you running with only 1 Folder?

Maybe when you copied it into another Folder it could be corrupted through the copying process so some Files are missing or something.

(U cuold also use the wiki or something for advice , do you've read the Guides and stuff?)