I just tried the exact same Export and it all worked fine for me - I dont know what is triggering that issue - I can ask - I tried 4 different machines with 4 different versions of GCS900 Software and they all were created first time.
If you reboot your PC and try again will it work?
Also when you updated t v 5.1 did you run the Cleanup Utility before installing the Release Version - because you had a Beta Version on your PC, there was something noted in the Cleanup Utility that some Machine Related stuff was not getting cleaned out by the Uninstall process - so the Cleanup that I posted on Monday is needed to clean out your PC before installing 5.1 - I would also try that to see if that clears the issue.
Alan