Just putting this up there in case any others run into the problem:
Had a Ford F-350 Powerstroke in the shop that worked AOK, and then for some damn reason it wouldn't turn all the way over, it cranked fine and made all the normal noises, just wouldn't fire. We were just about to tow it out and have a shop inspect it when I remembered most, if not all Fords have an inertia switch in them.
The inertia switch was located directly behind the passenger kick panel, it was triggered, I racked by brain trying to figure out how the hell it could have been triggered and realized my bodyman was making an adustment on the A-Pillar with his slide hammer, must have triggered it! Hope this can be of future help to someone out there!