I'm a bit of a networking noob here, so please bare with me.
Device: Linksys WRT54GL
Firmware: DD-WRT Version 23 SP2 (9/15/06)
Description: I installed Call of Duty 4 onto my PC. Everytime I attempt to log onto an online game with CoD4, I completely lose all internet connection. I do have port forwarding setup for this game using the proper port (port 28960, both). This only occurs with this game. No other games cause this issue (i.e. Starcraft, America's Army, Team Fortress 2, Mythos, etc.). When I remove the router from the mix and just use my DSL modem to my PC, everything works perfectly.
To this point, the only method that I have figured out to get my internet connection back up is to reboot both the router and the DSL modem, but obviously this does not fix the cause of the problem.