I dont wish to say your wrong but I thought I would just say that I have all of the above !!

I use Norton, Soundblaster live and ATI and I have them all running during gameplay. I am also on 56K and while playing I use Roger Wilco to chat. I also run behind a firewall and have remote console running on a seccond pc which shares my connection.
I bet u think I just lag out all the time?
On some servers I do but on most servers I can play fine after some minor adjustments to rate and snaps. I admin a server (with PB) which we have spent alot of time setting up and with all this going on I can normally get a ping of 250 and the game plays very smoothly. Most of the cable modem players which join our server rarely ping over 150 (unless the server is at its 20 player limit).
I may just be lucky.....