Mt. Gox didn't let you withdraw real currencies other than JPY, most interestingly the dollar, from approximately last August. This meant that when you were selling BTC for USD, you were actually accepting a USD liability of Gox -- Bitcoiners sometimes called them GoxBux or GoxUSD. It's a number in a database and now, apparently, something which you'll eventually be allowed to assert as a claim in their liquidation, but it is not actually a dollar.
The failure to allow withdraws in currencies they supported is why many people were speculating that Mt. Gox was insolvent, for much of the year prior to them admitting insolvency. As it turns out, we were probably right.
The failure to allow withdraws in currencies they supported is why many people were speculating that Mt. Gox was insolvent, for much of the year prior to them admitting insolvency. As it turns out, we were probably right.