This happened to me at first as well. I averaged around 535GH/s at v0.95, and after upgrading to 0.96 it dropped to around 490-495GH/s or so.

BUT...

I've been running it for over an hour and a half and I've stabilized (for the last 30 minutes or so) at an average of 549-550GH/s. So far everything seems to be running just fine, though I'll keep an eye out and edit this post if anything comes up.
Maybe it just needed to warm up for a bit?