Completely agree with what Roberto (and many other agents below) are selling. You could try refi first, and if that doesn't work, THEN you could go for shortsale again (even if you didn't get a permission first time). The prices are going up, and many buyers are willing to pay extra, so you might not need a shortsale at all. Also, even though most agents don't want to bother with less than 3%, you may find others willing to work for less commission (mostly newer agents, just to get their name out there and to get a closed sale).
One point that many didn't mention, are you keeping up with your payments or falling behind? That could make a difference in the bank's decision about shortsale, because they have to see and calculate whichever will be less of a loss to them.