USB wireless adaptor on Celeron 366 = S-L-O-W does it need a faster processor?

I've finally managed to get my wireless adaptors talking to each other
again and now I have a new problem. With an 11Mbps connection I'm
getting a MAXIMUM network utilisation of 0.11% :-( needless to say
it's pig slow. Even some web pages are timing out because they take
too long to load.

I was wondering how much strain the USB adaptor is putting on the
processor, it seems to be negligible as CPU utilisation rarely rises
above 25%.

Both adaptors are set to auto negotiate speed and both report 11Mbps
connections.