Filmstrip is skipping over photos when I use Auto Advance to Reject photos?

I'm trying to quickly go through and reject photos I don't want by using "shift + x" to reject them from my filmstrip.  Instead of advancing to the next photo I'm having a situation where Lightroom will jump ahead 3,4, sometimes 8 or so photos ahead when I hit "shift + x".  Does anybody know why this could be happening?