This is caused by one of 2 things.
1. The temp files used to create the reports are currupt. You can just delete
these files and the reports should work. Use windows explorer and delete the
directory C:\tmptopaz. This directory will be re-created automaticly when
Topaz is started.
2. One of the files that is used to generate the reports from might have become
corrupted or damaged. Use the Reindex Program, that you should be able to
find under your Topaz Data Directory, and verify the data files.
How do I reindex a database file?.