What's the brand & model of your router? If it supports UPnP, have you tried using that option within tools > options > advanced > firewall config?

When you port forwarded, did you set up a static IP first? Also, did you make sure that LW's listening port & the port forwarded were the same number?

Have you tried changing to a higher port number (eg 64049)?

Just out of interest, who is your ISP?

Have you double checked that the XP firewall is off?

When you deleted preferences, did you also check for a folder in the old location of C:\Documents and Settings\your username\.limewire?

If you have SP2 installed, are you using one of the connections patches?