I know this is an old post, but if, like me, you've only just discovered this site due to stuffing up your D70 and are searching desperately for any help, I thought there may be somebody who might benefit from my recent experience. When I say "recent" I mean "just finished fixing my camera 30 seconds ago".
I think I had the exact same problem and same cause as Leon (poster of the original question), i.e. non-working camera due to reconnecting LCD ribbon cable but forgetting to take out the battery. The original reason for dismantling the camera was to replace the faulty CF card slot.
Thanks to another page on this site (Camera dead, is there a main fuse?) I located two possible blown fuses. F1 in the diagram was fine, but F2 was blown. Rather than try to locate a replacement for the fuse and fiddle around trying to replace it (it is tiny!) I used a bit of a kludgy fix - solder a single strand of very thin wire across the two ends of the fuse. Yes, I know the fuse is there for a very good reason and shorting it is not good practice, but I reckon that as it hasn't blown before without me doing something stupid (see above) then there is little chance of serious harm happening. The worst outcome would probably be a dead camera and I had that already! The camera now works just as well as it has done for the last 8 years.