I have the same problem....I withdrew yesterday and it still hasnt arrived! nearly 24 hours now.....nothing. Not in the blockchain at all. 4.72BTC. This is ridiculous, Mtgox are so terrible..... support tickets go unanswered not even 'allocated' to a customer service rep yet.
Sorry to hear that, but being optimistic is a good thing and those BTC will show up soon, like OP's BTC.