Ok so I became a member of this forum just to share this with people in the hope that it would help someone else out.
I have Vista, McAfee, the latest version of Limewire and used IE to connect to the internet. I have a wireless connection which I share with my roommates.

I installed Limewire and it worked fine for a few hours. Then all of a sudden I lost my internet connection. Not only did this affect me, but it kicked all my roommates off the wireless too! (they don't connect thru my computer or anything like that). This cut me off from the internet completely- not just when I had limewire running. I uninstalled limewire and McAfee and it still didn't help. Not only did it somehow kill my cable internet connection for me and my roommates, it didn't let me on my school's wireless either.

I called gateway technical assistance and was told that they HAD DETERMINED the cause of these problems: its not McAfee, its internet explorer. He said that I had to call my ISP (time warner) and ask them to send a 'hit' to my cable modem. THen I could use limewire fine if I used Firefox and not IE. I was skeptical because that made no sense to me, but I did it and it worked. I haven't reinstalled McAfee, but he claims that I can run McAfee and Limewire together just fine if I use Firefox. As odd as that sounds, he said it was because of the way IE used java... Well he's been right so far and my internet connection works now, so I'd trust him.
Hope this helps.