It isn't an error, it is cause your wallet probably has a lot of "dust" (which is really small amounts) so to protect the network against dust/spam and a lot of small inputs, the fee is huge.
This shouldn't be true. Look at what the OP wrote:
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I transfered bitcoins from mtgox to my wallet. no problem.
now I have 0.5762188 BTC in my wallet. I tried to send these (ALL OF THEM) to another wallet.
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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.