Well stay away from Mt Gox until their USD accounts get sorted out, and they might not. The only well established fiat exchanges are Coinbase, Bitstamp and btc-e. However Bitstamp and btc-e were both taken down from DDOS attack over the past 48 hours. So far I am not aware of anyone losing funds though. Coinbase has been suffering other issues recently though, due to high transaction volumes.
I'm not sure you are going to get the answer you are looking for. There aren't any completely reliable exchanges out there, and these semi reliable exchanges all have some form of restriction.
solid advice.