Gox could be screwing over their customers in two easy steps.

1. Buy a bunch of BTC for $250.
2. Move them to another exchange and sell them for $600.

The owners of Gox obviously aren't bound by the "no withdrawls" rule.

Maybe this strategy could make them solvent again.  Maybe they are screwing their customers for huge profits. Maybe they are too incompetent to even see this as an option.