Bike fit issues would be my other thought.

I'm still trying to figure out what helmet I need, though. I'm wearing a Bell (discontinued model, I think). It's not uncomfortable, but I wonder how much of that is the fact that it's my helmet and I'm used to it. Every other helmet I've tried has in some way been uncomfortable, with the possible exception of the Giro Ionos. Scattante--too round and shallow. Louis Garneau, Giro, Bell--can't put my finger on it, but doesn't feel right once it's adjusted properly.