Hi David,
Sorry you have had these experiences, and most of us have felt the pain of something similar with various applications, not just Opus.
However, I find Opus Pro 05 quite stable and haven't had a problem opening an imp file for a couple of years, during which time I
have opened thousands of imp files.
A bit more detail on the usual things will give others a guide on how to help you.
Your setup, what you have been doing to cause problems, your style of making pubs, etc.
Reinstalling Opus might help, or trying to open the files on another PC.
The only way to get peace of mind working with ANY application is to back up files on a regular basis.
I didn't do backups on a regular basis until I lost a month's work once, so I know how you feel
Paul