Upgrade installation - user is logged out every page

I upgraded from 3.4.1 and had problems with the database, even after
running the 3.5.1 upgrade.
I did a clean install as a test to a new database. RT is up and running,
but the user is logged out after clicking every link. I see this messge
in /var/log/messages

Apr 21 18:49:11 server7 RT: Attempt to free unreferenced scalar: SV
0xa706bc0 at /usr/lib/perl5/site_perl/5.8.0/Apache/Session.pm line 616.

The server is ES3, and all the perl dependencies were satisfied by
installing RPMs from DAG.
Any help appreciated.

Chris Mason

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