Apparently the new version of Ubuntu broke compatibility with a lot of wifi adaptors, including some relatively new USB adaptors. If you have upgraded to 9.10 but are having problems seeing and/or connecting to your wireless network you may want to try the following:
1. Open the update manager
2. Click the settings button
3. Click the updates tab
4. Check the “Unsupported updates (karmic-backports)” checkbox
5. Open a terminal and type (and reboot):
sudo apt-get install linux-backports-modules-karmic
