just to note: both Jessie beta 1 amd64 images (20140316 and 20140802) suffer from this. As a workaround I use at the moment http://d-i.debian.org/daily-images/amd64/daily/, which starts the installer (serial console is broken) at least. In the last months I noticed the missing kernel modules besides amd64 also with the sparc architecture in wheezy. Thanks, Hermann