MtGox is notorious for not including fees when they are required by the network, especially if you clicked the "green" option. Not much you can do, if the priority is under 57,600,000 and there is no fee, it is considered blockable spam by nodes.
Is there a way to see priority? I just closed out my armory wallet (crashed too much for me), so there are like 20 input, it didn't include a fee - but total is ~1.5btc. thoughts?