many thanks to mpotter and others who have patiently suggested various changes so I could get a clean install of oa2.17.
As far as I can see I was suffering from various resource shortages. So I used a different server and got a good basic installation. For what it's worth, this is what I did that worked:
unpacked the 2.17 installation tarball in the document root
ran install.php
increased the php.ini memory limit from 32 megs to 192 megs
restarted httpd
blew out on a memory allocation error configuring the site after a successful install
increased the memory limit to 256 megs
restarted httpd
returned to the site configuration page and hit F5 and
successfully configured the site.
I've been able to log on and create a user and so on.
It looks very good.
The server that worked has Centos 5.10, 4 opteron cores, 2G RAM
Dave