A screenshot of the field which you want to change in WebUI or SAP GUI I belive will help. Anyway, if you are trying to upload the language as Arden already pointed you must check if is in internal or external (ISO) format, english = E (internal) EN (External-ISO) Spanish = S (internal) ES (External-ISO) all this information can be checked trough the T002 table.
Cheers!
Luis