Apparently they had delays in February of days.
I'm new to Bitcoin and posted a Stack Exchange question about it.
Here is the transaction: https://blockchain.info/tx/1c12a9f7db650956e3c01d7cd86fe8b4dd281e4d5dfc98f00af90803b158024f in case anyone can look and figure out what caused the delay.
According to blockchain.info the transaction was received at 2013-08-18 02:42:49 UTC and was confirmed at 2013-08-18 02:45:29.
That computes to less than 3 minutes to confirm. I suspect that Coinbase was delayed in transmitting the transaction to the network. You could try asking their support about it, but I doubt you'll get a satisfying answer from them.