Installation problem with 5.12: complains about mysql version

I've upgraded old yacs to 5.12 successfully, but I can't seem to create a new site based on 5.12.

When I access

http://www.morison.org/family/forum/setup.php

(with yacs mv'd into the appropriate family/forum directory) I get a page that says:

First installation

ERROR: YACS requires at least MySQL version 4.0. The server runs version 4.3.9.

Check MySQL version again

I'm not sure where it gets the 4.3.9 because:

/usr/sbin/mysqld --version
/usr/sbin/mysqld  Ver 4.0.18 for suse-linux on i686 (Source distribution)

so the version that yacs is picking up isn't quite right, but in any case, it's >= 4.0.

I'm blocked in bringing up a new yacs, so help is appreciated.