When installing the client adapter on a machine running Linux, it does not find the airo.o module. You will get this message if the airo.o file cannot be found in the modules directory.
While the name of the module is actually "airo.o", linuxconf is looking for "airo" and will know to look for a file ending with .o in the modules directory. Make sure that the airo.o file resides in /lib/modules/2.2.16-25.uid32/pcmcia/airo.o. If it does not, go to your PCMCIA-CS directory and rerun the make config, make all, and make install procedures as directed in the ./cwinstall script.