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A couple of weeks ago my Senao 2511 CD PLUS / EXT2 card stopped playing nicely with my own wireless network at home (I use it on a gentoo x86 system). My network is hidden and uses WPA-PSK for encryption, and until some time ago wpa_supplicant was working without problems. However, when trying to associate the card with the network i ran into this problem:

ioctl [PRISM2_IOCTL_PRISM2_PARAM] Operation not supported

After some searching the web, I was quite sure that I needed to upgrade either my hostap-drivers or the firmware on my wireless card.

Most of the more advanced techniques to crack wireless networks use packet-injection, either to produce more traffic in case of WEP cracking (replay attacks ) or to de-authenticate a connected client (in order to sniff the re-authentication handshake for WPA-PSK cracking).

In any case, the stock hostap driver doesn't allow you to inject packets, so I had to patch it.
You can get the patches here. Be sure to pick the right one for your card/driver. I used the hostap-kernel-2.6.18.patch which also works on my 2.6.19-beyond2 kernel. After applying the patch to the kernel sources, i did a make && make modules_install and rebooted the box. After that, injection worked great, but my card seemed to pick up much less traffic than before

When running kismet before, within seconds i could see dozens of wireless networks, but now only once in a while a new network appeared on the screen. Since the injection itself worked, I was quite sure I applied the patch correctly. After some research, I learnt that the injection patch can lead to problems if you use firmware that is rather old (although no precise version number for what is "too old" was mentioned anywhere).

Read my post here on how to upgrade the firmware on prism2/2.5/3 cards.