After trying a few different methods, I finally got my wireless connection up and running on my Ubuntu system, I just have to run this script every time I start up:

modprobe ndiswrapper
iwconfig wlan0 essid [SID]
ifconfig wlan0 up
dhclient wlan0

Every once in a while the connection will cut out for a minute or so, which also happens to XP machines on my same network (could be the router or just a problem with the DSL itself)... but, the XP machines will recover and regain internet access a few moments later. Unfortunately, I have to reboot my Ubuntu system to regain access. This usually works like a charm, but it's a pain in the butt to reboot every time.

I've tried re-running the above script after the connection cuts out, or running the individual commands. But, 'dhclient wlan0' gets to:

DHCPREQUEST on wlan0 to 255.255.255.255 port 67
DHCPREQUEST on wlan0 to 255.255.255.255 port 67
...

and never gets:
DHCPACK from 192.168.0.1
like it should.

If anyone has any idea what might be going on here, or how I could reconnect to the network without having to reboot, that would be awesome.
Thanks.

Also, the connection seems to cut out more often when I am running Azureus (bittorrent client). Think that is just coincidence, or are they related?

Regarding your connection, you might want to look into a firmware change for your router if you've always had this problem. I have a Dlink DI-524 and never had a problem with the original 1.03, then went to the 1.05 firmware and had constant disconnects. Went back to 1.03 and it was fine again. Now there is finally a newer 1.11 which has fixed the problems that 1.05 had.