We have experienced the same problem and it is a problem that we didnt use to have a year ago. Everyones autocad "hangs" for a random amount of time at what seems like random intervals. Some days it is more than others. Only Autocad hangs and the computer is NOT frozen. We have about 8 cad machines. I am ussing a Buffalo 2TB NAS for our storage, which I though might be the culprit, as far as handling all the traffic. But I have to rule that out because nothing else freezes except ACad. I disabled SheetSet Manager autoupdates which "seemed" to help but the problem still exists. I will try the AV extension filter mentioned above.
Did you ever resolve the original problem in this post?