When might "monitor mode" not work?
 

I would be interested to know what the status is, regarding wireless cards and monitor mode. I appear to have a wireless card which is happy to go into promiscuous mode, but which doesn't accept:

iwconfig wlan0 mode monitor

It returns:

"Error for wireless request "Set Mode" (8B06) :
SET failed on device wlan0 ; Invalid argument."

Anyone have any ideas about whether this is a hardware or software problem? Thanks

Most likely the hardware driver.

Some drivers are incomplete or do not have this capability (such as ndiswrapper).

Oh, that must be it then, because I'm using Ndiswrapper. Thanks for the fast response.