Copied from
http://en.wikipedia.org/wiki/WRT54G :
"As shipped, the Linksys firmware crashes under heavy peer-to-peer network traffic, such as BitTorrent. The reason for this crash is that Linux'sconnection tracking by default keeps track of old connections for five days. This five day limit quickly overwhelms the router when there are a high number of network connections, such as with BitTorrent, and can only be resolved by power cycling the router. For a detailed tutorial on how to permanently fix this issue on a pre-v5 router see the uTorrent FAQ[15]. Briefly, it involves installing a 3rd party firmware.
Earlier versions of the Linksys firmware (<4.50.00) have a bug that causes interaction problems between players in World of Warcraft.[16][17]
Some unconfirmed reports have also been made that users cannot use VPN, specifically PPTP connections, through the new version 5 router.[citation needed][citation needed] The best guess is that the router does not support protocol 47 (GRE) even though Linksys claims VPN pass-through support on the box.
The v6 firmware revision 1.01.0 introduced a problem where the QoS page requires a valid manual upstream bandwidth value even if the upstream bandwidth is set to Auto. [18]"
Try updating your firmware and stopping (not pausing) torrents which are queued or finished.