Try to use SQL profiler to find out the SQL statement which causes the crash. Some time ago we had crash with an invoice date in the year 2090 or smth. Even though it is within the range of SQL server supports, it caused the crash.
The register for Order Classes is common for Sales orders and Service orders. When I set an Order Class to create an Activity - it works for Sales Order, while for Service Orders - not. Is any setting...
