If you have a 64 bit version of Windows Vista such as Home Premium (and I presume 64 bit versions of Windows 7) you need to disable Driver Enforcement during boot:
Press F8 until you get a B/W screen ("Advanced Boot Options").
Arrow down to the bottom of the screen and select "Disable Driver Signature Enforcement" and press Return.
MS does not allow one to manually approve unsigned drivers in Vista 64 like they did in most versions of prior OS's, and until they approve AirNav's drivers we have to deal with this. While there are other methods that involve command line arguments or utility software downloads, this method works well, does not involve questionable software, and, as long as you don't boot often, is pretty simple. It is an effective stop-gap...
According to other threads AirNav has submitted drivers to MS for approval but it takes time for them to get signed. Once those drivers are signed by MS and released to the wild this issue will go away.
