it sounds like you're already getting a solution, but for anyone else who has this issue and can't load a previous save, here's an easy fix: open up the game's folder to \Graphics\Pictures and rename Viruark_AnalProbe_02.png to something else, then go do another event that displays a special cg, then rename the file back to the original name.
basically, the game is trying to display Viruark_AnalProbe_02.png over top of everything but dialog boxes, so by renaming it you make the game unable to find that image. this results in the game playing normally, so you can go about your business, except that Viruark2 will be missing a cg in the event viewer. but if you save it like that and rename the image to its original name, the game is still trying to display it, so you'll get your screen blocked again. if you do another event that displays a cg, though, then the game will replace the Viruark one with the one appropriate for the new event, and it'll stop displaying when the event ends as normal. if you save and revert Viruark_AnalProbe_02.png to its original name after that, then you'll be able to play the game normally and still be able to view Viruark2 in the event viewer.