Problems connecting to windows network Via Airport (Asking for Username?).

[Sleeping_Faster]

Apologies for the no doubt all to familiar question'

However, I am presently trying to connect to my companies network via the Airport card in my iBook G4.

The Wireless access point is a 3Com 8250 (802.11g), upon enabling the Airport I recieve a request for username as well as password.
While I'm aware of the password for the network I haven't been able to discern a username for the wireless network point and therefore have been unable to connect.

When encryption is totally disabled I have no problems accessing the network.

I believe the protocol being used is WEP (or at least the password / username prompt would imply as much).

Any help of advice would be much appreciated.

Cheers

(A rather newbie mac user)