I have had a functioning system on wheeze using grub2. I did an upgrade to Jessie according to the debian docs. Now when I boot my system I simply get a black screen after the POST screen - there's no GRUB screen or any hint of it.I had a similar problem with a laptop. I resolved it (finally) with a BIOS upgrade.Sadly this problem started AFTER I upgraded my BIOS. I have tried installing debian (AMD64) from scratch and am unable to boot from this either. I can't find any way to downgrade the BIOS and there is only one BIOS upgrade file on the Gigabyte website.
I have managed to make my system bootable by installing LILO. Could somebody let me know if this is likely to be obsoleted any time? I haven't received any indication that it will be.