I've entered a bug report for this problem - bug 557656 in Fedora Bugzilla https://bugzilla.redhat.com/show_bug.cgi?id=557656
. The Linksys WUSB v2.8 wireless adapter was working in Fedora11, but stopped in Fedora12.
There are actually 2 drivers that support this wireless adapter; at76_usb and at76c50x_usb. The later relies on the mac80211 module, which doesn't seem to work.
The solution to get it working is to blacklist the bad driver. This is accomplished by editting the file /etc/modprobe.d/blacklist.conf as root. Add the following lines to the file and reboot:
# wireless drivers