I was asked to set up wireless for a friend - fairly new Vista laptop, Sagem wireless router supplied by Sky - I could detect the wireless network on the laptop using the standard Vista wireless management, selecting it brought up the usual "enter network key", which is written on the underside of the router - the result every time was "could not connect to network" - my Blackberry 8320 couldn't connect either (wifi, connects to any 802.11b/g network that a computer will so far) - I verified that the code was correct using the configuration interface via Internet Explorer.
I had a spare known-working Speedtouch 585 in the car, fetched that, still no connection with either device. I unplugged a base-station for a cordless phone that was sited near the router(s), still no difference. I took both routers away, and connected first time at a different location using a different laptop, and my Blackberry.

The house is concrete construction, detached, no other wireless signals detected by laptop or Blackberry, the router was within a foot of the laptop with good signal strength - no metal surfaces nearby, or microwaves. Good, fast connection to the internet (I know the difference between a computer>router connection and a router>internet connection) and plenty of Vista updates done via a cable connection.

The router was set to "Auto" for channel configurations, which is something else to try changing, and the laptop was only just at the "ready to install Vista SP1" stage when I left - it could conceivably be a WLAN driver issue (Atheros), but connecting via my Blackberry usually rules out any computer problems in situations like this, and I specifically allowed driver updates including WLAN from Windows Updates.

There is another cordless phone base-station upstairs apparently, which could be interfering with the signal - I intend to turn that off when I return with the router to try again, but in the mean time I'm stumped - can anyone offer any suggestions?

From what you've posted, the problem does appear to be with using the hardware in that particular room. The routers and your Blackberry work OK in a different location so it does seem that there is something in the room causing serious interference with the signal. Presumably the phone's base station doesn't have a battery backup, keeping it active even if unplugged?

Can you connect to the router if the WEP/WPA encryption is disabled? What other electrical devices are there in the room, particularly any that are left on "standby"?

This really is clutching at straws because there is no obvious logic to the problem.

I think it might be worth unplugging all appliances in the house to identify what is causing the problem.

Battery backup, I hadn't thought of that. The router is in the corner of a large room, the TV and Sky Box are about 8 feet away and those the only electronic devices in the nearby vicinity, given that I haven't checked out what other devices there are on the first floor - I'll check for connectivity with encryption disabled and unplug anything that might interfere during my next visit - thanks for the suggestions.

Take the router off "auto" and set a channel such as 6, 12 or 2.

If you have Video Senders left on these can be a nuisance with interference too.

....and if the router is right in the corner with a thick wall either side to it it's not going to be at its best with the wireless signal .... try re-locating it just for testing purposes.

I got things working this time, changing channels from Auto to manual (I usually use 1,6,11) didn't work until both cordless phone bases were moved to the other end of the room (one downstairs, one upstairs). It's still not great - if there are still problems I'll see what results moving the router brings.
Thanks for the suggestions all.

You're welcome Brundle ...

lad the suggestions helped