Backup and restore

I have had this happen with some of our Blackboard courses.  Most of the time, exporting the course again solved my problem.  I had two times that it did not, and Windows XP's built-in compression couldn't even read the files.  I was able to use Power Archiver to unzip and rezip the courses, and then they worked.

My thought was just that something happened during the download to corrupt the zip, and it didn't seem to be Moodle's import that had the problem.

Thanks,
Matt