PC lags online, runs great offline

[Mightysauce]

I have been playing the offline mode of PSU for a little while now, both story and extra modes. The graphics settings i used were 1024x768, window mode, and "High end" graphics. The game play was crisp, fast and smooth.
Now I decided it is time to go Online, I get my guardians license, log in, dl all the required patches, and finally get in to play. The gameplay was incredibly slow. So, I log out and lower my settings. Log back in, still slow. I repeated this until I was running 640x480, 16bit color, "low end" graphics with all the settings to absolute minimum(compressed textures, post effects off, high/low LOD's to min), and still very choppy.
So I checked for new video card drivers, directx updates, performed bandwidth tests(scored above 2.0 mbs) and still no improvement. If anyone can help me, I would forever be in your service. My computer specs are as follows:

Hp Pavivlon Media Center PC
AMD Athlon 64 Processor 3800+ 2.4GHz
1GB DDR SDRAM (PC3200 400 MHz)
ATI RADEON X1600 pro 512MB
Broadband Cable Internet Service

I just can't figure out why it runs so nicely offline, but online, it is just unacceptable, my team mates run 2-3 times faster than I do, by the time I aim and foie, the enemy is already dead. I use this same computer to play Quake4 and Everquest2 without any problems at higher graphics modes. Please help!

[Mightysauce]

Update, tried several more things with no success. Sega tech support had a few ideas, but nothing really helped. Then I unistalled my firewall, and everything is fantastic, except now I dont have a firewall running. It wont work with the firewall disabled, or all the settings set to allow all traffic. It only works with the firewall off the computer entirely. I ran F-Secure btw. If anyone has any suggestions for a firewall that does work, that would be great!

[Dhylec]

I use Zone Alarm at home & it works with the game. It's free. Try it if you feel vulnerable.