Thanks for the answer.
We have cleaned our data using the sql-Collation.
I think it's not wise to have Data with NUL-bytes in a
varchar-Column, because other Transact-SQL-functions have also
problems.


For example the LIKE operator is also inconsistent.

SELECT 1
WHERE CHAR(0) LIKE '_'

Yields:
<nothing>

SELECT 1
WHERE CHAR(65) LIKE '_'

Yields:
1

By using the collation you suggested, the LIKE Operator worked as
expected.

There must be some enviromental COLLATION setting, which is
database-specific, but i didn't find it in exported-scripts from the
enterprise manager.