It sounds like that 0.5762188 BTC is a single transaction from MtGox in a single output.
nicofan, you can confirm this for us if you post the bitcoin address from your wallet here. We should be able to look in the blockchain and confirm that the 0.5762188 BTC is a single output and not made up of many really small amounts.
This sounds like a bug in the MultiBit software. If the amount really is a single output, then the fee requirement shouldn't be more than 0.0005 BTC. Once you confirm for us that the 0.5762188 BTC is a single transaction with a single output, I'll cross post this to the MultiBit sub-forum so you can get an answer as to how to fix it.
OP has to confirm that, but I thought maybe many different transactions because Mt Gox has deals with mining pool so they can dust the blockchain and not have to pay large fees.
Agreed. It's difficult to make an educated guess as to the cause of the symptoms being described without additional information.
nicofan, Please provide the bitcoin address (or addresses) from your MultiBit wallet so we can confirm that it isn't filled with hundreds of tiny outputs from MtGox or from activities such as SatoshiDice or "free bitcoins" websites.