I've got the following wireless card:
Intel Corporation Wireless WiFi Link 5100

It's a pretty new one, so I hope I supports the master mode. But when I try to execute the following command:

daniel@daniel-hp:~$ sudo iwconfig wlan0 mode Master
Error for wireless request "Set Mode" (8B06) :
SET failed on device wlan0 ; Invalid argument.
Ubuntu also created an interface called wmaster0 but there I can't set anything. I'm using Ubuntu 8.10.