There has been an update released for UAG it is available from
During my installation of this update I was sure that something had gone horribly wrong. After a few minutes it had seems to stop responding and was stuck about 75% done. No errors no CPU activity nothing to indicate that it was still busy...
Just wait for it to finish. My lab machine took about 15 minutes to finish the installation of the update.
So don't panic - just wait, and wait and wait