Short of bashing my head against the office wall upon being repeatedly confronted with a 404 Not Found error, I realized that I was using the wrong path for RewriteBase in .htaccess file. The exact error was:
The requested URL /home/oxid/pubweb/4_2_0/oxseo.php was not found on this server.
Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny4 with Suhosin-Patch Server at 192.168.253.129 Port 80
If anyone faces this on your OXID installations, this could be your fix, too.
We were using:
RewriteBase /home/oxid/pubweb/4_2_0/
Instead we should have been using:
RewriteBase /oxid/
… where the target URL is http://192.168.253.129/oxid/, (being used to put together a Debian 5.0 Lenny Virtual Machine for OXID 4.2)