Webuser Forums: Network surfing difficulty

I have a home network setup using a Linksys wireless router, all PCs are running Windows XP Pro. The host (which has my Broadband connection attached) and one client pc are connected by cables to the router and the second client is a laptop using a wireless PC card.
The network works fine and I can share files and printers no problem. However, I cannot surf the internet or download mail using Outlook on either of my client PCs, something I used to be able to do until recently (Not sure whether someone or something has been fiddling).
Tne Internet Gateway appears on both client PCs so I know the connection is there and working and I get regular 'New Updates are ready to download' messages, but IE6 nor Outlook are somehow not being able to use it.
I have run the network troubleshooter without success, all IP address settings appear OK and I have pinged all my PCs until they are sore. When I tried to log on to messenger on a client PC, I got an error message saying my proxy settings are missing or incorrect, but all my IP address settings are set to automatic.
Does anyone have any ideas??

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