What killed my campaign? Mr Freeze

Firstly, the campaign crashed when all text was blotted out by what seemed to be a black marker. Thereafter, sometimes EB has made my computer crash whilst loading but more recently has started to freeze midway through a battle. After turning the computer off, and on again, I am informed the some files have been corrupted and the computer repaires itself. I then load up EB again, try to fight a battle... and it freezes. Does anyone have any idea what this is/how to fix it?

Particularly frustrating if your playing a 'nigh-impossible' faction on VH/VH!! 3times I've been on the cusp of a great victory only to have it robbed from me by the computer!

This sounds like a hardware problem. You should run Memtest overnight (google it), and also scandisk. Have you installed new video drivers lately? Does the crash still happen when you start a new campaign? Also, running a validation can't harm.