Thomas,

> It was some illness in his code. Not closing the result set and
> the statement in a finally block, where the connection in the
> finally block *is* closed (returned to the connection pool).

This should be a bug in that pool. According to the JDBC spec on
connection.close() all statements are closed (and result sets are
closed on statement.close()). Post a bug report to the pool developers.

Best regards,
Roman Rokytskyy