Installed Linksys Wireless-G PCI Adapter WPC54GS

Howdy Mike-d. here,
(Disclaimer) I usually just file Bug and answer a few questions.
One option is this link to an answer I just gave, but I actually use this card and configure it by left clicking network icon and manually configuring by left clicking on manual, make sure there is a check mark in the wireless section, click on properties and uncheck enable roaming mode choose Local Zeroconf Network (IPv4 LL) from the configuration drop-down menu, then left click o.k., then close. Right click network icon in upper right corner taskbar and left click connection info-if you got an IP address great, your there, if not you might try to reconfigure or restart computer and /or router first.
https://answers.launchpad.net/ubuntu/+source/hal/+question/25190
Good Luck, If you need more info, ask for more info.
Mike-d. out

Typo "sudo lshw" in terminal to see the list of detected hardware detected and associated drivers. Does the wireless card show up? Is there any driver attached to you card? If card is present and driver is attached, type "sudo iwconfig" to read off the state of the card. Generally this card should be handled by one of RAlink drivers. Which driver depends on the chipset (can be seen in "lshw" output).

Also, if you have good connection, as a sanity check you can try downloading livecd (8.04 say) and seeing whether your wireless card works under in livecd. If yes, there is at least some hope.