I've always suffered with car sickness and the NAS website suggests that this could be due to issues with balance (it's listed as part of vestibular over-sensitivity).
However, I find that it's not just car travel that gives me motion sickness - it happens with video games too (which is really annoying because I do enjoy playing them, but I find myself feeling like I'm going to be sick after about 20 minutes!).
I'm curious - does anyone else experience motion sickness? What triggers it for you?