the culprit seems to have been in my for each loop. Strange it didn't occur in the other programs (option strict) gave me the clue. Here is what it those lines look like now:

'Concatenate the part number and description columns and display that so the user does not have
                'to figure out what just the part number is

                shieldblocks_dt.Columns.Add("concat")

                For Each item As DataRow In shieldblocks_dt.Rows

                    item("concat") = item("PartNumber").ToString & ", " & item("PartDescription").ToString

                Next

I simply added the .ToString and all was well