[TYPO3-linux] Cannot login to BE when source outside document root

[Paul Vetch]

Hi all,

Having a bit of a nightmare trying to get Typo3 (4.05) going on a new
server (running CentOS 4.4 (i.e. Debian), with Plesk; PHP 4.3.9; MySQL
4.1.20) 

Typo3 installs happily, and with the source installed in the vhost
document root I can login to the BE.  I want to share the source between
vhosts though.  If I move the source out to /var/lib/typo3/ and set
open_basedir appropriately, I can run through the installation with no
problem.  However I just cannot login to the backend, even if I create a
new BE admin user.

I've checked and the BE users are being created properly in the DB (and
I'm running MySQL 4.1.20, not 5 which I know has a known issue in this
regard.) 

The problem is the same under PHP 4.3.9 and also in PHP 5.1.4.  Could
this be a session problem of some kind?  PHP reports no errors. I hope I
am missing something really silly.

Any advice appreciated.

Paul