Mt Gox Bitcoin exchange is withholding bitcoin transfers so that it can force down the bitcoin price on it's own exchange.
It is doing this so that it can buy bitcoin at a below market price and escape the losses it would otherwise incur as a consequence of its shoddy accounting system.
There's no doubt about it - this is a form of theft.
Mt Gox already has solved the "tech" problem it had but because its owners were off driving around in their Maseratis instead of managing their business while they were fleeced of most of their funds they are now trying to save themselves from serious litigation by buying cheap to pay back the BTC they allowed to be stolen.
They say they have their clients BTC in safe wallets but it's a lie.