Personally, it has never happened to me, nor have I heard any reports of that although I have found that it is a good idea to not do anything else when it is updating or scanning but I've never had any kind of freeze. While you are waiting to see who else responds to this, MSAS has a newsgroup (forum) that you might want to browse for issues. If you click on the general tab on the left at this link, there are 114 pages.
At the urging of my Department's computer support guru, I installed MSAS a couple of weeks ago. Ever since then I've had unexplained periods where the system simply "freezes" for up to a couple of seconds -- occasionally it's a hard lock that requires hitting the reset button, something I've never had to do before installing MSAS. Is this a known problem? Any fix for it?
Thanks -- Dave K.