Sorry that it took so long, but we should have a working version:

Download and install the debian package from http://jenkins.grml.org/debian/pool/main/g/grml-rescueboot/

This will generate a slightly different grub.cfg which should contain all necessary dependencies in the 
live-media parameter.

You will have a iso image which supports the new generated live-media parameter, you can use 
http://jenkins.grml.org/job/grml-medium-amd64/102/artifact/2011-06-13_03-16-27/grml_isos/autobuild_2011-
06-13_03-16-27.iso which is a 64bit medium grml.