Linksys WRT54G was a "lemon" in that the firmware had bugs but Linksys never fixed it. So yes, port forwarding at least improves its functionality. Wireless connections are not as reliable as wired when it comes to heavy p2p use.
When changing versions of LW, it may be a good idea to remove the LW firewall rule and re-add to the firewall. And only have one software firewall active.
WHen upgrading to Pro, always a good idea to delete the LW preferences folder whilst LW is
closed; instructions here:
Point #2 & 3 in Fixes for Limewire (sample image included at bottom of page.)
There 'might' be some useful tips in these links: (a)
If LW Will Not Connect,
__ (b)
Problems with the search,
__ (c)
Hostiles List
hmm I am also wondering with the WRT54G, it might be a good idea to re-boot the device when changing LW versions. Just a thought.