Another snag I hit was forcing dhcp to assign an IP to my card automatically. Under Knoppix I used pump -i wlan0, but for Kubuntu I needed dhclient wlan0 (coincidentally when I was using Backtrack 2.0 to asses my network encryption it required dhcpcd wlan0).
Using Backtrack though, dhcpcd kept hanging so I used killall
modprobe -r ndiswrapper
ndiswrapper -r bcmwl5
This way I could install the driver again. Phew!