Account Schedules Error

As I select "Create New Document" for Navision to export my cash flow to excel, I get the following window message:

"The transaction type cannot be changed after a transaction has started. A transaction starts when the first database operation, such a FIND, NEXT, INSERT, DELETE, MODIFY, SUM, and COUNT, is run. The error occurred because the transaction type has changed from UpdateNoLocks to Snapshot."

Any help advice on this message would be greatly appreciated!

Christian