Using iw to add a virtual wireless interface, getting the error "No such device (-19)"

I am trying to add a virtual wireless interface to my debian squeeze system using iw.

The output of iw list is shown below:

root@alix:~# iw list
Wiphy phy0

I am using the command:

iw dev phy0 interface add wlan1 type station

to add the virtual interface wlan1 however this gives me the error:

command failed: No such device (-19)

If I use the command:

iw dev wlan0 interface add wlan1 type station

it passes fine however if I try use both wlan0 and wlan1 I get an error saying neither are unique and so that doesn't work for me.

Anyone any ideas what could be causing this? Thanks

About the first error you get ("command failed: No such device (-19)"): You can either use

iw phy phy0 interface add <name> type <type>

or

iw dev wlan0 interface add <name> type <type>

As long as the physical names and the device names don't clash, you can also omit the phy/dev keywords and simply use

iw phy0 interface add <name> type <type>

About using both interfaces at the same time and the message about them not being unique:
This is probably because they both use the same MAC address. You can try to change the MAC address of the new interface before activating it.

ip link set dev <dev-name> address <new-mac-address>

A word about your interface modes:
My iw command (v3.4) says

Valid interface types are: managed, ibss, monitor, mesh, wds.

Not sure what "station" will do.

Also, if you're trying to operate the two interfaces in different modes, make sure your wlan card supports this:

iw list
[...]
Supported interface modes:
     * IBSS
     * managed
     * AP
     * AP/VLAN
     * WDS
     * monitor
     * mesh point
software interface modes (can always be added):
     * AP/VLAN
     * monitor
interface combinations are not supported

Notice the last line.