On an XP machine executing scheduled tasks or when a scheduled task starts, The error is returned .
"The application has encountered a problem.
We are sorry for the inconvenience. Access violation at adress 05427A78 read of adress 05427A78"
The Windows Task scheduler is not working or it is been blocked by a domain policy.
Toad depends on the windows task scheduler for running scheduler task
(Control Panel > Scheduled Tasks)
Ensure Windows Task scheduler is working by running some test scheduled task.Check with your system administrator that there is no policy blocking the Task scheduler.