Running as admintrator is not required, however you have to be in the netmon users group. If you've just installed you will have to log out and back in for this group membership to take affect. But logggin in as admin is a work around if that hasn't been done yet.
As for the missing NIC, the Netmon driver needs to be bound to the WIFI NIC in question. You should be able to look at the properties of the NIC and see if the driver is bound.
If this is an upgrade of Windows 7, then you'll have to rebind all the NICs. You can do this by running and administrative prompt and running "Nmconfig /install". If this doens't fix you problem, please let us know.
Paul