My chain is falling off the back and that is sad
 

I have a Truvativ rouleur GXP crankset. Whenever I am in the small chain ring and the bigger rear cogs (like the biggest 4), the chain will fall off after a couple rotations of the crank. At first I thought it was the limit screws or maybe the way the front derailleur is positioned, but then I looked over it and they seem fine.

I think that the chainrings may be bent slightly. Are there any other possible causes?

Are the chainrings bent?

Don't know. I don't have the tool to take the crankset off, so I'll have to wait until tomorrow when I can head to the LBS.

But I have a few friends that are mechanics at that shop and they are baffled :(

Doesn't take a tool.

Take the chain off the rings and spin your crank while watching from a fixed point (I like pressing my head to the seat tube and looking down; it gives a stable reference).

If the chain rings are bent you will see them "wobble" while the crank spins. If they are not bent the rings will run true.