ab1451,
I would suggest you download and install the latest version 4.03 off the Radarbox support page when it comes back online again, other than that you should be OK.
I would remove the existing version first and if you are using a version of Windows from Vista onwards, install to c:\Airnav instead of the default location to avoid windows virtual store problems. You will need to install the Navdata file again and ensure you install to the correct location as the existing Airnav 2009 data folder will still be there unless you manually delete it.
Alan