You cannot copy and paste a lookup field in a datasheet in Microsoft Access 2010. Additionally, you cannot copy and paste a row or column that contains a lookup field.
This problem occurs because the Access Services datasheet does not correctly handle the copy and paste operation for lookup fields. Lookup fields typically have two values: a bound value that is the foreign key to another table, and a display value that users can see. This problem occurs because the datasheet tries to paste the display value into the lookup field. Instead, the datasheet should paste the bound value into the lookup field.
To work around this problem, click the cell that you want to paste into, click the drop-down arrow to expand the combo box, and then paste the lookup field.