Linksys WRT54G Wireless Broadband Router - the XP and Mac Drama!

Hi there,
I¹d appreciate any help.

I recently bought a Wireless Broadband Router made by Linksys. I was told it
would work with Windows XP (Home), but probably not with my Mac.

I followed instructions, and set it all up. Amazingly, it works seamlessly
(and without configuration) with my Mac, but not with the PC. I spent two
hours on to Linksys support, checking and confirming the configuration of
both the unit and the PC. Now, it picks up the wireless connection for a
short while (maybe 5 minutes) and then drops it. I have tried it with the
firewall on and the firewall off, but it¹s the same.

My Windows XP machine works without any problems at all on other wireless
connections (e.g. In coffee stores or train stations).

Has anyone had a similar problem? I¹d really appreciate some help!!

Kind Regards,
Patrick