Thanks all for the replies.
the pc that the usb extender is attacthed to is an old dell gx270 so i dont think it even has usb2.0 as standard.
As for watching the company test it and sign it off,no i was not there unfortunatley i am only there for three hours per support session,im not a resident technician.But i was told by the IT co-ordinator that they had left it working.I doubt that very much!!!
I will try to see if its a usb 2.0 problem,and let you know the outcome.
once again thanks for your advice.