This problem has been happening and I don't understand it.
I'm using windows xp with a roadrunner cable modem and a lynksys router

I open up a bunch of web pages in Firefox, and then all of a sudden, no
websites are available. I get the browser error message "
could not be found. Please check the name and try again".

I don't get any windows connection messages.
If I try in internet explorer, I still can't connect.
I can email fine from thunderbird.
I can't ftp anything.
I can browse fine on my localhost.
If I reboot the router and the modem, it doesn't help.
If I reboot the computer, I get the connection back, for a while.
If I repair the local area connection it seems to complete the repair
but doesn't help.
If I disable the connection and reenable it, it doesn't help.

What could it be, and failing that, is there any way to reboot the
connection without rebooting the computer ?