I can understand that they may be fiat broke but how can they have fewer Bitcoins than their legal transactions indicate?
You send me 10BTC.
I lose those BTC by some means.
You ask for your BTC back.
I say I have halted withdrawals of your BTC because $PROBLEMS
You say, "it's OK, grifferz must have my BTC because trades have indicated it"
I sit on a big blue ball.