The problem was permissions on /home/user not /home/user/public_html

I have not spent the time looking into details, but I booted up the old server (fortunately I had not blown away the drive content yet), and looked at all the directory tree.

The permissions for /home/user was drwx--x--x

The user that I was using on the new system was the one created by the post-install, first boot process. Its permissions were:

drwx------

Other users that I created with drwxx-rx-r

So I changed the new system's user directory permissions to match that of the old system, and everything is working.

Just one more footnote about installing a new Centos 5 system, check the user directory permissions.