If you get the below Microsoft .Net Framework error (An Item with the same key has already been added) when trying to add a Mapping to your template, it means that that there are duplicate values within you Raiser's Edge that is causing a conflict.
More often than not, the duplicate values are often found within a table associated with the mapping you are trying to add.
Have a look with your Raiser's Edge tables, specifically the table relating to your mapping area and try to identify any duplicate entries that are present.
Next, use the Table Clean up tool within your Raiser's Edge to remove the duplicate.
