This blogger have succeded in getting a D-Link DWL-G650+ Wi-Fi adapter to work in Ubuntu and have been so nice to write it down for us
If you have a similar problem, the solution might be here
The installation went smoothly, and Ubuntu runs beautifully, considering it's an old 800MHz Celeron. Except for one small issue: My D-Link DWL-G650+ 802.11g cardbus adapter wouldnt work. The status LEDs would come on, and the adapter was properly detected by the OS, but I couldnt manage to get an IP from the router.