After an afformentioned power-loss, one of the guest-vms started BSOD’ing during boot. Safe mode was no go, and only recovery worked.
Found a tip:
– Copy ‘C:WindowsSystem32CodeIntegritybootcat.cache’ from a working, similar server (2008R2 in this case) to a cd or usb-drive.
– Since this was a Hyper-V guest I created a ISO with the file, using ImgBurn, and mounted the iso inside the guest, while in recovery mode.
– Delete the original bootcat.cache from the system, and copy the working one you got from the other server.