Hi,
I'm having the same issue. I just purchased BIAB Pro upgrade, and am trying Realband for some basic stuff.
I can save the file in wave format, but when I try to save as MP3 I have exactly the same issue as above.
Is it possible there's an issue with the mp3 converter that Realband uses? I'm running windows 7 64 bit (Pro).
Thanks!

- Russ