> The problem arises when I try to get a connection from the pool. The
> pool is configured with setMinPoolSize(1) and setMaxPoolSize(1) to
> avoid problems with mutiple connections, as I don't know do they
> exist.

You can use multiple connections from the same JVM. Release notes contain
information about this issue - it is safe to use multiple connections on
Linux, driver provides necessary synchronization on per class-loader basis.
So, you have to only ensure that firebirdsql-full.jar is loaded by the
top-most classloader (e.g. system classloader).

Also check the log files, you should find more information there.

Roman