This message means you have an inventory record that you are trying to upload that has a "NULL" value in the lot field. The Lot field in our inventory table cannot contain a "NULL" value we normally place a default value of "---" in this field, but for whatever reason that default value is not being written to the table. You will need to look through your upload data and find the offending record and put a value in the Lot field. This value can either be a valid Lot value if you are using Lots in your system or our default value of "---".
Dan
