We are not BitInstant (or whoever you bought bitcoins from). Contact them.
I just tried to deposit some funds into Mt. Gox as well. Afterwards I went to check my balance and noticed it hadn't changed. Apparently they changed all the account numbers and I was not aware of this, so my funds were sent to the old account number. Not sure if this affected you but it may be something to look into. Hopefully I can get my money back, I emailed support but apparently it will take 3 days to get a reply. Hopefully the price doesn't move too much at the beginning of this week.
MtGox waits for 6 confirmations.