Depends on what you are trying to update to. It has to be camera raw 6.x. Anything else and it will not work.
Kindlt confirm the current ACR version from, Help->About Plugin->ACR,
ACR Installer logs
Program Files(x86)\Common Files\Adobe\Installers
/Volumes/%Volume Name%/Users/%Username%/Library/Application Support/Adobe/AAMUpdater/1.0
You can zip all the files together and send us through mail. This would help us in finding the root cause.
Appreciate your help. Apologize for the inconvenience.