Are you using the Linksys router in wireless mode?
Were you downloading torrents or just regular files found on gnutella network?
Reason I ask is that model router has reknown firmware issues. It is unreliable when run in UPnP mode. Secondly, wireless is even less reliable, especially for torrents where there are many more messages & connections passing to & fro. Speed drops, & possibly even loss of connection from the internet all together.
I'd recommend port forwarding your WRT. If you wish to do that, there's no specific instructions I can find for OSX unless you go to Linksys support site. Here's a starting point.
1. Most important step is this very first step & must be done first!
Setting up Static ip on Mac OSX
2.
Port forwarding for Linksys WRT54G. You should use the 'BOTH' protocol representing both TCP & UDP, which you will see near bottom of that page. Which port to choose? You can choose the one suggested which is the default for LW, 6348, else choose any port between 49152 - 65535 because they are the least likely to be blocked by ISP's. Both LW's connection & listening ports should be set to be the same.
Oh ... that site still uses the old LW 4 example advanced page at top of their page; see this one
Manual port forward instructions & sample image for the settings within LW. But otherwise follow their router instructions below that.
After port forwarding, you may need to reboot the router. At least reboot the computer.