Hi Kurt,
I've heard similar reports before, of Frontier/Win being unable to read a file through File->Open yet able to load it if it's opened through the Explorer. I don't know what to tell you, since Seth and I were able to open the file both ways. We both used NT4 machines, as it happens, with Frontier 8.0.5. We used WinZip and StuffIt Expander for Windows. But I think we know that the GDB file itself is okay, since you were able to open it successfully.
Perhaps there's a Win2000-specific problem with Frontier? Can you produce the same effect trying to open any other GDB?
-Brian