When is a connection not a connection

When is a connection not a connection?

I just come back from a customer who can?t connect to his BT home hub 2.0 wirelessly

In the Microsoft connection to network screen I can see the laptop showing a connection to the hub (80%) strengh but when I open IE I get BT internet fix it message.

If I use the Ethernet cable I can access the internet, so that rules out the ISP.

Specs o/s vista, acer laptop,
If I use my own laptop I can’t connect wirelessly to the hub.

Any sugestions how to over come this problem ?