Gnutella Forums - Connection Winds Down, Stops Then Locks Out

Hi there, this is a first post for me. Im new to Limewire and have had a look through the postings for a similar problem but theres nothing so I'm hoping that someone can help me with a fix...

I'm running XP Pro with SP1 and have a DSL connection @ 576kbps.

When I first loaded Limewire and started downloading a file everything was fine... for a while.
I was 75% through a large download with a nice connection speed when I noticed that the speed was slowly winding down, from 52kb in increments until it finally stopped at 0% then Limewire disconnected.
Also, I it seems that my connection locked up or something as I was unable to connect to webpages or download email - as if my connection had been cut - but the DSL status said I was still connected.
I closed all pages, Limewire and the DSL connection and tried to connect again. This time I couldnt connect and got Dial-up Networking error 721.

The only way to get my connection working again was to restart the pc. I also had to disable Limewire from loading on startup as this constantly locked me out.

I have McAfee VS/Firewall set to allow all, and the XP firewall has been setup to open the Gnutella port. I have also tried to connect with them both disabled to see if it makes a difference, but no luck.

My ISP claim they dont block the software and said it may be a Dial-up networking issue. I had the same problem running WinMX.

Can anybody help me out please?