As far as I understood (as in, read in some other threads), withdrawing a certain amount (say, 1k$) of funds from MtGox is a major bureaucratic PITA because of all the ID and stuff they require (that's actually what refrained me from even trying their service so far). The thing that puzzles me the most is that given that bureaucracy, the least you could expect in return is them fixing such erroneous fundings with mismatching IDs a bit more promptly...