Not sure I understand this fully.
Is it impossible to withdraw Bitcoins from MtGox to another exchange?
It seems weird that the price is dumping.
The basic gist is that most investors believe Gox is going to go bankrupt and it's better to have a claim against them in fiat than in btc -- so people are dumping all they can, and at this point, at whatever price they can get.
And that's correct -- can't withdraw in either fiat or BTC, thus further driving the panic.