I know how you feel mate!
I have a Linksys WAG54G Router and mine works for a hour or so or longer then it looses it's connection or blocks it.
The first I know of this is when clicking to a diff page and then I get the 'Page un-available' page.
Everything seems to indicate that I'm still connected but it's no go.
The only way to re-enable the connection is to go to Network & Dial up connections and right click the 'Local Area connection' and click DISABLE. Then right click it again and click ENABLE. Then go to the Lnksys WLAN monitor and then go to profiles and click connect.
Then go to 'Site Survey' and click connect.
Then click refresh.
This ususualy re-establishes the connection, though sometimes I have to all the above two or three times in succession before it will play ball.
It's really pissing me off!