Hi,please backport autotools-dev (20100122.1) to lenny. It provides a debhelper sequence addon which allows for automatic replacement of config-{sub,guess} in sources via "dh $@ --with autotools-dev", similar to the way quilt quilt (0.46-7) introduced "dh $@ --with quilt".
The package is a no-brainer and simply needs to be rebuilt. Cheers, Fabian