I installed ReSharper Beta 6.0.2165.98 and it was working fine. I updated to 6.0.2168.356 when prompted. It appeared to install correctly, but ReSharper is now missing from VS2010 (Ultimate Edition). There is no menu item for ReSharper and it does not appear in Options. It is not in the Extensions Manager and it is not in Help > About.
I ran devenv /Log and I can see no attempt to load anything to do with ReSharper.
I've also installed RC 6.0.2171.226 version with the same result (installation completes with no problems but not available). Trying to reinstall ReSharper Beta 6.0.2165.98 doesn't help.
Any ideas of what I can try?