WLAN Boot Problem

Hi guys...
I have just purchased 2 WLAN cards @ 11MBPS, and they connect to my PS's
via USB 2.0. Both machines run Windows XP Home and had no obvious issues
installign and setting up the network, however, when i turn the PC's off for
the night and then turn them on in the morning (turning on the host machine
first) it does not inatilize the WLAN card, the only way windows realises it
is there is if i pull it our from the USB port, then plug it in again. The
same also happens on the seccond machine. Once i ahve done this, the devices
connect together and network is all ok, but why does Windows not recognice
the WLAN cards on boot up?

Any advice on this issue would be much apreciated! Thanx in advance!