My guess is that they'll give you a negative balance, assuming you withdrew all of your funds. Then, at most, they'll request that you pay them back, but not really do anything outside of Mt. Gox besides that request (In other words, I doubt there would be Dwolla chargebacks or reversed bank transfers).
However, I would expect a full ban from them in that case. You can probably keep the money you transferred, but then they'd be insane to let you keep trading at the site or avoid the negative balance by starting a second account. It's their prerogative to allow people Mt. Gox access, and this would be the only real incentive to encourage people to pay them back without potentially breaking laws.
But that's just guessing. I so do love it when we all have to guess at these rather important questions.
Edit: MagicalTux just said this in IRC:
<MagicalTux> kgo: when you'll recover your account the coins amount will be negative and you won't be able to withdraw until you either add coins back, or buy coins
You also havent understood what i mean.... i wanted to withdraw money from my US Dollars... i didnt wanted to withdraw BTC's! The time i requested the withdraw to a Bank Account i had 0 BTC and an amount in USD in my account at Mt Gox... I also had an OPEN BUY order but i never thought that it will get executed. So my question is ... i dont have problems if the buy is reversed BUT what is with my money? my USD? will the withdrawal request still be there? And if not will my money credited back to my account?