crank bent?

I wouldn't say defintaley the crank. A couple questions:

1.) Has it ALWAYS done this?
2.) Have you gained significant weight or strength sice buying the bike?
3.) When was the last service with an expert set of eyes?

Point1: Is the bike flexing? How stiff is it? If you can flex the frame, you can cause ghost shifting. This can be a significant issue with full suspension mountain bikes and, to a lesser but still possible degree with any bike. Lightweight, low spoke wheels can also flex making the chain want to move as the wheel flexes.

Point 2: Relates directly to ponit 1, except YOU have changed in weight or strength and are now flexing the bike.

Point 3: Could the rear derailleur hangar be bent? Could the bottom bracket have spun loose in the frame? Could the chain rings be worn to the point where they don't hold the chain well?

IIWY: Take it to your trusted LBS and have a mechanic go through it. If possible, take a ride with the mechanic and illustrate the issue so they can see it happen.

No, not always. I wrecked a couple of weeks ago (on the component side) and did a tri a couple of weeks later (didn't notice it then, but I was not in a higher gear most of the time and was not really paying attention to the shifting so I could have missed it) That said, I'm generally (read: never) not in my top gear, so I suppose one could argue the point that it isn't a big deal, but, the perfectionist in me is slightly bothered, and, I don't want the problem to spread to the front derailleur/etc.

I've lost about 40lbs since I bought the bike, so it isn't my weight, and although I am producing more power, I don't think my average 18-20mph is sufficient output to flex the bike or crank. I wouldn't call the S32 the stiffest bike I've ever been on, but it's no noodle either.

Rear Derailleur and bottom bracket are fine.
If the rings were worn, I imagine I would be having the problem in gears other than the very highest few.

The bad news is... there's not a lot of LBS' I trust around here. I usually end up with a lighter wallet and STILL have to fix the bike myself.

Thanks for bringing that stuff to my attention, some things in there I hadn't checked.

on second thought... possibly it is the bb. As soon as I'm off work I'll check it for sure. Anything to avoid when removing my crank?

Nah, pretty standard stuff. If it's an ISIS interface, you can hold the tool on the BB by placing a quick release lever through the tool, the BB spindle and tighten. Then take a big-honkin crescent wrench to the tool and spin the BB out of the shell. Or if it's really stuck, place the tool (while mounted to the BB in the frame) into a vise and spin the bike frame for leverage.