I recently upgraded the wireless network card in my Ubuntu PC from an 802.11g to an 802.11n.

Now, it can't see my router. It doesn't appear in the list of networks that is displayed when you click on the NetworkManager icon in Gnome. Other networks are listed and I have connected to them (no password required!).

I'm using the Windows driver through ndiswrapper and it can see the card. I tested the card in a Windows PC and everything worked.

The router's log doesn't show any messages coming from the wireless card.

What have I done wrong?

If you need any more information, just leave a comment and I'll get add it to the question.