[Hampshire] Help with Router?

I have a wired network around the house, (several computers and a LAN
printer,) based on a SpeedTouch MODEM/Bridge and an 8-port Netgear switch.

A while ago, I decided to add a wireless option and bought a LinkSys WRT54GL
router. This is supplied with documents (.pdf) and a setup 'Wizard' (.exe
files) on CD. I tried to set it up manually with Debian Etch, but without
success.

Having recently acquired another machine which has XP installed, I decided
to see what I could learn by trying the W*nd*ws wizard. Everything proceeds
as per the documentation until the end: 'Cannot access the internet'. If I
unplug the router and replace it with the switch, everything's fine.

I've run out of ideas. If I was to bring the kit to the November meeting, is
there some kind soul who would take a look and perhaps tell me what I'm
doing wrong?

(For now, I'm assuming from the router's responses that it's not faulty.)

Chris.