You are not alone. Its worse than you think. As I understand it its going to
take a very long time to rectify. Open an APAR - give IBM a real hard time.

If you have NT workstations which are built with a different code page than
the server they save files on then you have a potential nightmare on your
hands. The scenario we hit was US English build servers and Kanji build NT
workstations. Any time a user on the Kanji workstations saved a file with a
filename containing characters from the Kanji character set we ran the risk
of the backup failing. We hit exactly the assertion failure you see but only
in a dialogue box when running the GUI - dsmc did not give us this
(3.1.0.6).

As a workaround we have recommended a Kanji build workstation running the
ADSM client backing up the servers drive via the UNC of the servers drive in
the dsm.opt domain statement. The ADSM client does not have a problem this
way round as the US English ASCII is a subset of the Kanji codepage. You can
probably see quite clearly that this is not an arrangement that we will be
able to live with for long.

Regards
Alan