Check the install logs of that succesfull installation.
Pay special attention to the storage device.
I don't believe the issue is with storage device - it's "installation device" - the storage (/dev/sda, sdb, and sdc) exist and are accessible in the VM. I believe that the kernel being loaded is missing the NIC drivers for virtualized environment for some reason. The NIC devices aren't being created, so the TFTP/HTTP content aren't available after the initial pxelinux bits are served.
I'm investigating why the vmlinuz kernel isn't able to create the NIC devices. The hypervisor is using the good ole standard e1000 NIC driver. I've tried e1000e, virtio-net-pci, and a handful of other virtualized NICs that my hypervisor supports.
has the /dev/sda replaced with information from the succesfull install.
I do recall something like /dev/xda seen on a VM. I might be wrong
about that. If it works report back. If it doesn't work surely report
back with install logs of both (the succesfull manual one and the failed
preseed one).
Yes, in some cases virtualized hardware devices will show up as /dev/vda. But not in this case. Thank you.
~~shane