After trying just about everything, I finally stumbled upon a solution.
If you have multi-bootable partitons, you need to mark your Windows partition as "Active". Here's a guide on how to do this: http://windows.microsoft.com/en-au/windows/mark-partition-active#1TC=windows-7
You got my hopes up - I tried yet again - and it STILL fails. This has now been months of no fix - and my gut tells me the only option is to reformat the machine. With Windows 9 rumour for the 2014 Build conference going beta - my plan is probably going to be wait till that comes out and reformat for a new OS on that.