Help needed, a netbook has me stumped

[A Place of Light]

I've been given an advent 4211c to sort out and it's got me beaten. I can't get the wifi to work and it's driving me crazy as to what's wrong with it. I can turn the wifi adapter on (Function key then F11) and the thing not only sees my wifi netwoork but also connects to it.....it just won't pass any data through the connection. Connected, signal strength excellent etc etc but it just won't up/download data. It works perfectly with a network cable plugged in, but this wifi issue has me scratching my head over it.
Any ideas?