From the Ndiswrapper WIki card list:
Looks like the Ndiswrapper module should work for you. If you decide to use it, follow the detailed Wiki closely for installation. There are instructions for using iwconfig to set modes, encryption keys etc in the Wiki too.
http://ndiswrapper.sourceforge.net/phpwiki/
There are some Distribution-specific bits of guidance in the wiki somewhere - you may find something helpul for redhat
Cheers