Just yesterday I was taking a look at my girlfriend's bike, a Schwinn Wal-Mart MTB, and she was complaining that the front shifting isn't working. Specifically, I can get the derailleur to move the chain between the chainrings, but as soon as I let go of the shifter it automatically drops back down to the smallest ring. This is on a bike equipped with SRAM GripShift parts.

So any suggestions apart from the obvious (buy a real bike)?