I've attempted to troubleshoot this problem myself for a couple of days now, but since this isn't exactly my area of expertise, I figured I'd try a post.
I have DSL service with a gateway 2wire wireless modem/router.
I have two laptops that are running Windows XP and Windows 7 that are setup with wireless and work fine.
I also have an xbox 360 connected via wireless and a playstation 3 connected via cat5.
The problem is that I have a desktop that's running Windows XP. I just got around to setting it up, (just moved) and at first it worked fine, but was running slow due to the programs that I had set to launch on startup. (utorrent, aim, msn, etc) I disabled several of them and restarted. Upon restart Firefox wouldn't connect to the internet, and neither would internet explorer. AIM, uTorrent, Safari, etc works.
Firefox and IE give "Unable to Connect" messages when I launch them. The only solutions I could fine through troubleshooting were making sure Work Offline wasn't enabled, it's not. And make sure auto-detect proxy settings is enabled, which it is.
Did you check your router by loggin on to the webpage set up, to make sure that HDCP is enable or that any other settings are fine? If you see all your settings fine, try to reset the router by turning it off, unplug it and the press and hold down the reset botton for about ten seconds the turn it back on, because since you move it could be that the router still has the old network settings from your previous ISP.
If it is enable and still cannot connect, try resetting the router like I explained. One question though? On your post you said "I have DSL service with a gateway 2wire wireless modem/router" does this mean you have two wireless routers on the same network? Forgive me if I didn't understand it correctly.