duplicate key error

Hilmar Buchta explains in his Blog A duplicate attribute key has been found when processing… some common reasons for duplicate key errors in processing error messages. The most likely reasons are:

• NULL values in the attribute key column.
• data that violates the attribute relationships defined in the dimension.
• A third reason is that there are separate key and name source fields for an attribute, so there is more than one name corresponding to a key.
• A related issue results from collation effects: distinct string values from an oracle source are considered as duplicates by SSAS because they only differ in capitalization (upper/lower case), trimming or some strange characters (as the german "ß" that will be replaced by "ss" or "ä", "ü", "ö" etc.).