Sherlock - the only other thing that I can think of is that this may be yet another symptom of the dreaded Virtual Store problem in Vista and Windows 7. Are you running either of these, and if so, did you install the program in the default Program Files folder?
If the answer to both of those questions is Yes, then for the long term, you might be best to reinstall RadarBox in a different folder like C:\Airnav
Rod