This error may occur for several reasons. Please try the following options:

1. Close down Cashbook and re-start the computer. You may need to force quit Cashbook to do this. This can be done by simultaneously holding down Ctrl + Alt + F12 keys on the keyboard or via Task Manager. View: https://support.practicalsystems.com.au/Articles?id=651
   
2. Add Cashbook as an exception to your Anti Virus (Norton, AVG, McAfee, etc) software and restart the computer
   
3. ​If the error still occurs, please contact Practical Systems