Why is Captivate not letting me open a published, saved file?

Aaaarrrrrggghhhh! What the what? I spend hours preparing a simulation and can't open it even though it is saved, and published!
The error suggests that: the file is open - it is not; the file is damaged with an example that it was an email attachment - it was not; the hard drive doesn't have sufficient space - it does; and the system doesn't have sufficient resources, as other applications may be open - they are not. This has happened before. Is there a way to get this file open?