Wireless woes

A customer of mine has a wireless network at his place of business, and most of his computers are networked though it.The problem I'm having is with his laptop, I can't get it to see the wireless signal, at first I thought it was the built in wireless card so I plugged in a wireless adapter, setup the software, but still nothing. I then took the laptop back to my workshop and to my surprise both of them worked fine on my wireless network. Could someone please explain to me what would cause this. Both networks are of the G variety, just different brands. His router is a Linksys and so is the wireless adapter I plugged in so I don't think compatibility is the problem. So those of you who have more insight than me, I could sure use your help.

Did you try to manually set up the wireless connection versus auto-detection?

Does the router have Mac filtering on? SSID broadcast on? Using same channel?

A little more info would be helpful.

Is it XP Vista or Win7?
If it is XP Right click the icon choose View avaliable wireless networks.
The left bottom Advanced.
Then at the top Wireless Networks
Remove every connection in there and reboot.
Try to connect again.

CCT Yes,Forgot to check, Yes and Yes

Ferrit Been there done that

This computer has been on his network before but it needed a little help at times, now it just refuses to see the signal and it's never done that before.

Have you tried removing the wireless card from device manager and rebooting?

Ferrit I did try what you suggested and more, but nothing seems to work.
The thing that has me stumped is that both the built in card and the external one can't even see the wireless signal in my customer's office, yet in my shop they both logged on to my wireless network. Why one and not the other? All his other computers can log on, and I even tried my own laptop and it had no problem logging on to his network. What sort of setting on his laptop would block one network signal but not the other?

would the laptop happen to be a HP?

No it's a toshiba P4 with XP

Remove the preferred network that already exists and then view available networks and find his and connect to it.

Just in case anyone is interested I finally got the laptop to see the wireless signal. I downloaded the latest driver and it worked.

Thats great news. Likely an update from windows update broke it.
Everytime i try to use the windows update for my wired realtek from windows update.
I end up looseing the internet and having to do a driver rollback.