> Maybe, if that problem persists, but not right now, because I cannot
> decide this on my own.

Ok, but please keep this in mind. I would relly like to fix the bug if it is
there, and your case seems to be quite nice. Another possibility is that you
just prepare me a test case and example database that shows the problem in
JayBird 1.5.3, but works with JayBird 1.5.1.

> dataSource.setCharSet( "ISO-8859-1" );

Correct.

> dataSource.setNonStandardProperty( "sql_dialect",
> Integer.toString( 3 ) );

This can be ignored - it is by default 3.

> dataSource.setEncoding( "ISO8859_1" );

Correct.

> (The database has ISO8859_1 charset and DE_DE collation.)
>
> And I am still getting those "?" characters.

Bad.

> For right now I will stay at firebird 1.5.1, and if you cannot find
> a fix, I will try to make a test case at weekend.

Ok.

> As jaybird1.5.1 works, I suspect that this is not important, but for
> your information: I am running firebird 1.5.1, sun jdk1.5.0 and
> tomcat5.0.28 on debian sarge.

JDK 1.5.0? I did not test JayBird with JDK 1.5.0. Can you try running with
JDK 1.4.x?

Roman