I've got a Sony Vaio laptop. Until yesterday I had Windows 7 and Ubuntu 12.04 installed. Today I upgraded to Windows 8, which killed my OS selection screen. So I booted to Ubuntu 12.10 from a USB stick and ran Boot Repair. This recovered the GRUB screen and let me boot into my Ubuntu 12.04 installation, but now I can' boot Windows 8.
When I select the option that booted Windows 7 before, it looks like it wants to start Windows 7 (sic) again (black screen, with the text "Windows is loading" or something), but then reboots the machine after a few seconds.
I'm sure Boot Repair can fix this, but I know far too little about the whole booting thing to know the right settings for it.
Here's my boot repair report thing.
Edit: I really want to emphasize that it seems to be trying to start Windows 7. I'm pretty sure Boot Repair selected some old Windows 7 backup files. I already ran Boot Repair once after I installed Ubuntu. Maybe it's using some files or configs it created back then.