I'm not sure what to say...I haven't had any apparent problems, although I just checked out the Phoenix Labs website, and it does say that PeerGuardian conflicts with McAfee! Their recommendation is to use this firewall instead:
Outpost Firewall
They say the free version is quite good, however, if you want the quickest fix, I would just use your Windows firewall instead. I'm not sure how it compares to the other firewalls.
Here's how you would shut down McAfee firewall:
1. Open McAfee Security Center (double-click on M in system tray)
2. Select 'personal firewall plus' tab
3. On top, it will say 'click here if you want to disable personal firewall plus'
P.S. It is my opinion that Limewire may be slowing down your internet connection, not PeerGuardian (PG may slow it down a little?)...although PG will block access to certain sites. I just disable PG while the page loads, then turn it back on. If it is a site you use regularly, you can open PG and choose to allow access permanently (a little difficult to do).
Best of Luck