lock failed and buffer leak

testing the (postgresql 6.3.1 included) jdbc ImageViewer example.
It works. No errors.
But in the pgsql log I fond these (actually many more):
----------------------------------------------------------------------------
-----------
Apr 17 10:08:02 digital logger: NOTICE:  DateStyle is Postgres with US
(NonEuropean) conventions
Apr 17 10:08:07 digital logger: NOTICE:  buffer leak [65] detected in
BufferPoolCheckLeak()
Apr 17 10:08:07 digital logger: NOTICE:  LockRelease: locktable lookup
failed, no lock
Apr 17 10:08:07 digital logger: NOTICE:  buffer leak [75] detected in
BufferPoolCheckLeak()
Apr 17 10:08:08 digital logger: NOTICE:  LockRelease: locktable lookup
failed, no lock
Apr 17 10:08:47 digital logger: NOTICE:  buffer leak [65] detected in
BufferPoolCheckLeak()
----------------------------------------------------------------------------
-----------
what do they mean ?

Claudiu