Thanks to the team at First Class Accounts for passing on their experience with a downloaded update from MYOB. Could have been due to the file becoming corrupted during the download process.
After downloading and installing the new MYOB from the internet (Accounting Plus V18 or Premier V12), someone went to shut down her computer and found it would not reboot. Looked like the MYOB download had severely damaged her Registry. The IT guy repaired the problems, but not without 36 hours downtime on her system!!! He said that hers was the second system that he had seen with similar problems after downloading the new MYOB!!
I wasnt there to experience it firsthand, so I dont know if reverting to a previous system restore point could of helped (or indeed was the solution).
Another reminder though to ensure your critical information is backed up and can be restored – just in case a software upgrade turns nasty!!