Uwe,

Helen's post is 99% chance the problem you are facing.

If you have not defined any ODS 11 specific features (eg, index with
size over 250-something bytes, index on expressions), then you should
be able to use the gbak from the 1.5 kit against your 2.0 server. This
will create a fbk that 1.5 (or 2) can restore. Certainly worth a try.

Adam