> I have already tried to lowercase properties, but without success. I
> suppose it would be some tricky error, but I am not able to check
> what is wrong, because the error message is very general. As far as
> I understood there isn't possibility to use log4j for datasource ?
> Unfortunatetly Java system App server doesn't supprots JDBC driver
> only.

It turned out that logging is already there. You have to configure
log4j and specify -DFBLog4j=true as startup parameter for your JVM.
Depending on the log level you specified in log4j you will different
amount of information. Exception you are interested in happens on WARN
level, so probably there's no point to enable DEBUG. Looking forward
for your results.

Roman