Comment 2 for bug 97322

I believe you may have to shut down (ifconfig down) the interface before you can switch modes, which is why you get the "busy" message. I have (apparently) the same hardware, I think I have to do this and I've seen it elsewhere.

Although In the case of ad-hoc mode, I then get a "Operation not permitted" when I try to bring the interface back up again.

But then the native rtl8187 driver doesn't pick up the AP on my hardware at all, where Windows does, so somethings very wrong with my setup.