Yeah, that's how I figured out the problem.  It makes sense that a Yubikey that shows up as a keyboard would be caps sensitive.  Maybe if I would clean off my desk once in a while I wouldn't have stacks of paper flipping my CL button or holding shift.  Anyway, my experience will certainly help others.  I think highly of the Yubikey after using it for a few days.  Can't wait to try it after I forget to take it out of my pocket and send it through the wash.  It's only a matter of time...