Sounds to me like your mtgox account was hacked. By that, I mean you gave away your password to someone else and they took your money/BTC. Withdrawals to bank dont covert to BTC.
Its confirmed, I just lost 8 BTC through the MotherF**** MTGOX MY USD$ somehow mysteriously converted to BTC and transferred to an unknown address when I tried to withdraw to my bank account. THe odd thing is I even got a email notification saying that I logged into my account to initiate the transfer.