You are trying to open files that have been converted to the most recent version of Payroll or MultiLedger with an older version of the program. Locate the most recent version of the CheckMark Payroll or MultiLedger application and use that to open the files.
If you are running in OS 9.x, you may need to rebuild your desktop. Restart your computer while holding down the ‘Command’ and the ‘Option’ keys. You will get a message asking if you want to rebuild the desktop. Let go of the keys and click yes. This will take a few minutes. Once it’s done rebuilding, you should be able to open the files without the error message.