What happens if you connect using an Ethernet cable, rather than wirelessly?
Has this started happening since updating LW to the latest version, or did it happen with earlier versions?
Have you tried using an older version of LW, to see whether the problem's version related?
See whether you have the same problem with the Beta version of LW:
LimeWire 5.4.0 (Beta) - Lime Wire
If you can stay connected via ethernet cable, you could see whether port forwarding (rather than using UPnP) makes any difference.
You'll need to set up a static IP address for your computer first:
PortForward.com - Free Help Setting up Your Router or Firewall
Port forwarding instructions for your router are here:
Port Forwarding Limewire on the Belkin F5D7230-4
To find LW's listening port in LW5, go tools > options > advanced > super really advanced > firewall. Choose a port in the range of 49152 - 65535. Remember to click 'ok' to save any changes to LW's options.
LW's listening port, port in the 'manual port forward' box & port forwarded withih router setup must all be the same number.