It sounds to me like the DL creation did not complete. When you create a DL in Unity, it is then created in AD. It was probably partially completed and that is why "it already exists".
Open SQL Enterprise Manager and see if the DL exists in the UnityDb database\DistributionLists table. You can delete the row - be very careful with what you delete.
Search ADUC for the group name. It's name will be groupname+locationid and it's alias will be groupname. Delete it.
You can try creating a new group, group-type Distribution, Group-Scope Universal. Use SaWeb to import.
