Are you sure the scope is mounted correctly? tightened down and all that jazz? I know it's a noobish question but I had the same problem when my scope wasn't torqued down all teh way... a few clicks would send it way off base.

Secondly, were you benched the whole time? Picking up the gun, moving clicks and not settling back into the same EXACT position can have disastrous results, I know! HAHA.