Comment 46 for bug 32123

Just for the record:
Here the solution seemed to be to remove all entries containing pata_via from /etc/modprobe.d/blacklist.local
I probably had added it before in response to bug 213639 (or for some other obscure reason), though I couldn't remember it anymore.

I noticed I could start the new kernel by entering "modprobe pata_via" from the busybox command line and then leaving it via Ctrl-D, you should maybe try if that works for you as well to find the true source of the problem on your machines. The pata_via is only relevant on mainboards with VIA chipsets, of course. If unsure, boot from the live cd and find your used modules either with "grep ata /proc/modules" or "lsmod | grep ata".

I don't know if I had the same bug (doesn't look like an iniramfs problem any more) but the symptoms were very very similar, so maybe someone else might have been suffering from the same problem.