This error is a critical error. If this error is received then the application should be terminated immediately. No other TwainPRO calls should be made after this error is received. This does give the application the chance to do any non-TWAIN clean-up processing as well as inform the user that a critical error has occurred.

Possible causes:

The Data Source TWAIN driver executed an illegal operation, such as an illegal memory access, a divide by zero, etc.

System.Object
   System.Exception
      System.ApplicationException
         Accusoft.TwainProSdk.TwainProException
            Accusoft.TwainProSdk.DataSourceInvalidOperationException

Reference