A few weeks ago I updated to the ACR 8.1 release candidate.
With the release of the final version I have gone to the update in the PS CS6 help menu and the update fails.
My system is Win 7 64 bit Home Premium. I have not had any problems accessing updates over the past few months.
I know this isn't going to be any consolation. But I opened Photoshop CS6 last night, clicked on the updates, it indicated that there was one update, and it updated without a hitch.
Ok I finally got it done. In the AAM preferences I deselected all the applications except Camera Raw. Then it finally worked.