Unfortunately MadWifi support for the AR542x series in
ath5k is, to quote from the code, "a work in progress." I'd suggest that you get the
madwifi-hal-0.10.5.6-r3879-20081204 tarball from the
snapshot site. That's mostly the
ath_pci module, but it's a more recent release (3879) than the one you're using (3366).
The 2.6.26 and 2.6.27 kernels have been changing the wireless headers and structures so the MadWifi code has to be changed to correspond, and the older release you're using does not seem to be up to date. (The error you quoted is because the library function
skb_append was - I presume - changed or eliminated in the newer kernels.)
The rpm-fusion
madwifi package is, if I remember correctly, is based on the 0.9... code rather than the newer 0.10... code that supports 64-bit processors, so, if your laptop uses a 64-bit Fedora release, you won't have much luck with the
rpm-fusion RPM.