Dear Tangent
This error has only been reported for QIWIN or Adagio Invoices, and is associated with corrupt data, not a problem with the program - so re-installing will not help.
To confirm this, you can try opening a different dataset and see if the same error is returned. I would be surprised if it was. You can try sample data (x:\Softrak\QIWIN\Samdata\*.sam, where 'x' represents the drive where you installed QIWIN and/or Adagio).
If you cannot even open the dataset, then you will not be able to perform the Data Integrity Check - your only option would be to either restore from a recently made, good backup (prior to the problem), or get a database repair done. If you have a good backup, then you would have to rekey any transactions that were entered from that point on.
Regards,