Firefox and Thunderbird can no longer connect?

I have been using Firefox and Thunderbird for probably over a year now, and I've installed them on various machines and so on. I am a Web Developer and Computer Administrator so I know my stuff pretty well, but I'm completely stumped.

Today I was surfing on the web and suddenly my Firefox told me I couldn't connect anymore. I found that weird, tried restarting it, checking it on another account on the same system, tried Thunderbird, none could connect. I tried getting to my local IP address (I'm behind a router), it couldn't even find that, and it couldn't find my router either.

I removed my router, couldn't do anything either. I've turned off my computer and started it again, didn't work. I took an old copy of Firefox and installed it again (I didn't uninstall the other one, hoping it was ask me to repair), didn't work.

here's my specs:

Win XP SP2

Firefox 1.5

Thunderbird 1.5

I would prefer not to upgrade, as a web developer I need to have the most common browsers.

Firefox and Thunderbird can no longer connect?symatec

Check other internet functions first.... Start%26gt;Run 'CMD'

ipconfig /release

ipfconfig /renew

ipconfig /all

if a 169.something number shows up then it's not the browser. Sounds like a network issue to me - not software.