We currently have a cable modem with both usb and eathernet. We can get online just fine.

When we try to get online with the PS2 that is a different story.

When we direct connect to the modem we get a 611 Error - Cannot connect to DNS server.

We also tried to use a switch box which had the PC, PS2 and Modem all hooked up together.

When we tried that, not only did we get the 611 Error on the PS2, but we suddenly lost the network connection on the PC due to a conflict of IP addresses.

Any idea guys? And no we are not going to try or buy a router.
Is Call Waiting turned off? I used to play my PS2 online, and had the same error until I turned off Call Waiting.
In response to Dead_Demon
I have cable internet, why would call waiting effect it at all?
In response to Shades
I dunno, I have FiOs. It just worked for me, I figured it would work for you, too. It never did make sense to me, though...
In response to Shades
ok plug the plug from your ps2 into your modem thingy lol and then pull out the cord in the usb on the modem(if one is there) then unplug the power cord on the modem then plug it back in then try it...
Hmm. Is your Network Adaptor second hand? It's possible it's setup for someone elses network and you'll be able to fix it by factory resetting the network adaptor.
It doesn't sound like anything is broken, more like the router and Network Adaptor have conflicting configurations. It sounds like your Network Adaptor is trying to get a specific IP address that's in use by your PC.

If you're not too network savvy you could try disconnecting the PC from the network, then connecting the PS2, then reconnecting the PC. As long as the address isn't reserved for the PC that should allow the PS2 to get the address it wants then give the PC the next avaliable one.
In response to Yami_Marik0
Hey Yami Actully I read about that, so I took the PS2 and plugged it directly into the Modem and then I turned the modem off for 5 mins to let it reset and then tried and it worked.
I may have a solution.
You say you go direct, right? This looks just like your trying to bridge connection in Halo 2, if you were doing that. Heres something you should try before you buy that router.

Step 1)Turn off all firewalls
Step 2)Connect your PS2 into the back of your modem
Step 3)Go into your Network Connections. If you don't see your connections, on the left-hand side, there should be an option that says 'View all network connections'. If it has that option, click that. You will now see two connections, your LAC(which goes to your PS2) and your Broadband Connection. Highlight both connections, right click on one of them and select the option, 'Bridge Connections'. Now you should be able to play online with your PS2, but you won't be able to surf the net.

Hope that helps. If not, just go and buy a PS2 - Compatable router.
In response to Dead_Demon
I already told you I fixed it.
In response to Shades
Whoops, guess you did. Sorry about that :P