Whenever you try to do anything with documents it returns an "invalid class string" error (Wordperfect x3 only)
This occurs when Prevail cannot find the class id for the Wordperfect application. I put together a registry fix on userfilestoolsX3-WPO_OLE-Merge-WPx3-Fix.reg.
Close Wordperfect X3. Run the registry file. Agree to the windows warning dialog box that appears. Restart Prevail.