Odd speed problem

Hi, I have 512/256 ADSL and I connect to the internet via a 4 port ADSL
router. Connected to this are 2 PCs.

There is no problem when both are wired to the router.

I have recently added a USB 802.11b adapter to my desktop, and a compatible
PCMCIA device to my laptop. The idea is that if I unplug the network cable
from my laptop, I can connect via a wireless solution.

I have got the connection up and running using Windows ICS, but have very
slow download speed. The strange thing is is that my downloads speeds
(140Kbps) are slower than my upload speeds (190Kbps). What could be causing
this?

Cheers, Dave