Problems with large objects and 6.51

Hi,

did anyone of you ever saw some strange problems with large objects and
the postgresql 6.51?
Sometimes ago I want to switch from 6.4.2 to 6.5.1 and my tools, using
the large objects through the perl-library refused to work. lo_import
didn't work anymore.
I traced it down through the libpq, where I found that a test with
lo_lseek in the lo_open-function (file: fe-lobj.c) fails. Going deeper
into the source and drawing a trace of debug-output across some files I
switched tracing from the libpq to the backend.
Here I found in be-fsstubs.c, that after the function lo_open sets a
cookie using the function newLOfd, just this cookie will be cleared by
lo_commit, which is called by CommitTransaction (in xact.c). The handle,
handed out to the application by the library-function lo_open is now not
longer valid and the next access through this handle fails.

Did I understood something wrong in the source or is there a bug?

I attach the test-application (in Perl, named db_test), the debug-output
of the application (and the outputs in the libpq) (db_test2.log), the
debug-output of postmaster
(post2.log) and the files I patched with my debug-output (you will find
them easily because in every line I changed there is the string 'WN').

May be anyone of you, especially from the developing-guys, find time to
have a look into the attachments?

Thanky you,
Wolfgang