"Sales Header does not exist"

Occasional error now becoming more frequent… When posting a receipt/invoice on a sales order, user gets the error message, “sales header does not exist”. System locks up and does not recover. After shutting down Navision, user logs back on and invoice has posted. Any insights??

From memory, this problem existed in an early version of 3.60, but was corrected by a hotfix (9?). What version are you running?

We are running 2.6 Adv Dist flavor.