Erm 3 possible problems here. WRT54G is probably the worst model Linksys ever brought out. It does not work reliably in UPnP mode. Normally Linksys devices are very good(amongst the very best) but any model with 54 in it is not so good. If you're not computer literate then you don't want to do the to the firmware.

Optimum (OOL) is reknown to have problems with p2p sharing. Best bet is to use a high listening number. Go to LW's menu bar, Tools>Options>Advanced>Firewalls & change the listening port to 64049. Press apply & close & re-open LW.

ZA firewall. Make sure XP firewall is disabled. Go to the control panel, double click on Windows Firewall, check the disable box. Then configure ZA as described in a link at the very bottom of the page here (advisable not to have 2 active firewalls b/c they can interfere with each other); Firewall configuration instructions (click on link). Also see http://www.gnutellaforums.com/showth...threadid=38788

If still problems, try port forwarding your linksys device. You'll find a link for your model here http://www.portforward.com/routers.htm

BTW check out these posts by ELoXL
http://www.gnutellaforums.com/showthread.php?t=53091

http://www.gnutellaforums.com/showthread.php?t=52953