Hm, it might be that it worked for me with these images, not the d-i... If you fail with previous images try the ones from here:http://ftp.nl.debian.org/debian/dists/squeeze/main/installer-armel/current/images/iop32x/network-console/ss4000e/
I'm pretty sure all you need is working redboot, 2 right files and 3 commands in redboot. And use ymodem.
That might maybe explain why I had squeeze installed, not wheezy, which I tried but didn't do it.
Good thing is that after installing squeeze, you can add backports and install a 3.2 kernel, which works very smoothly, just apt-get and reboot.