Hello,
I'm having the same issues after the update. I'm using the official LL viewer. I've already tried uninstalling and installing it again, clearing cache etc but nothing. Lowering my graphics didn't resolve the problem either. It freezes when I move the camera, when I try to click any button, when I start walking, when I stop, when I turn around... I never had these issues before.
I've checked if it could be any other thing outside of SL, antivirus, other programs, other games... and they all work fine and don't interfere. I was close to format PC as the OP did.