Try the following in order:
1. In the Batch grid, select Tools, Edit Batch Setup from the action bar
2. On the Fields tab, group the Addressee/Salutation fields together using the Up and Down buttons on the right.
3. Click Data Entry to return to the batch

If the error still occurs:
Ensure there are no duplicate column headers in the batch.

To remove duplicate column headers:
1. Select Tools, Edit Batch Setup from the action bar
2. On the Fields tab, use the left arrow button in the middle to move the duplicate field from the right side to the left
3. Click Data Entry to return to the batch.