It's McAfee I'd say...Here is a thread that has been started by one of McAfee's Tech guy's he is looking for people's system specs as to why Mcafee-Limewire-Vista wont work....
Have a look at it, he offers a temporary solution...
Also I have provided a few links about other member's and their solutions for getting it to work...
http://www.gnutellaforums.com/genera...onnection.html