In Project Insight Version 12, we released our Resource Allocation Warnings and Notifications.
This feature allows you to:
1) Set an Error Message in the Administration > Project > Settings section
2) Add the columns "Over Allocations?" and "Over Allocation Discovery Date" to the task list
3) Receive emailed Auto-Alerts to let you know when an Over Allocation is discovered
Not mentioned in the video (oops!) - you'll need to enable Email Auto-Alerts in the Notifications > Settings section of the administration. Check out the check boxes below to demonstrate how often you want to know when there will be allocations: