You don't need networkmanager for wusb54gc.
I did a post here
how to install the necessary driver.
I'm currently using Kubuntu 8.04 (not 8.10 because of nvidia driver problems).
I also tested the live version of Kubuntu 9.04 (at the moment in alpha test), the good news there is that wusb54gc works out of the box, you can make a network connection via grafical interface (on the taskbar) just by selecting your wireless interface (wlan0) and fill in your WPA key.