Advantage Error Guide
Problem: An operation was performed that requires a nullable field. For example, this error can occur if AdsSetNull is called for a field that cannot be set to NULL. This error may also occur when executing an UPDATE or INSERT statement with a NUL parameter that results in an attempt to set a Visual FoxPro field to NULL. For example, using the Advantage Client Engine API AdsSetEmpty on an SQL parameter will cause a NULL value to be used.
Solution: Verify that the application is specifying the correct field. If necessary, restructure the Visual FoxPro table so that the field can be set to NULL.