> On creating the tables I did not specify any character set.
> Obviously the FB-Driver cannot handle this.

When you do not specify the character set, it is set to NONE.
However, driver tries to guess the charset using the system encoding.
This might lead to wrong results.

Try to comment a line #127 (might be different in your case) in the
org.firebirdsql.jca.FBManagedConnectionFactory:
...
// defaultCri.setProperty(GDS.isc_dpb_lc_ctype, charset);
...

And one more thing. Can you run unit tests? The build target
is "tests-report-html". If they succeed, then driver is able to
handle the situation you described, because it creates database for
tests.

Best regards,
Roman Rokytskyy