You might as well revert back to a previous/ov assembly or drawing file. I've gotten that error a number of times and realized that it results from something that I just did, or added to in my work flow: such as a mis-derivation in a part or the creation of an erroneous view. Most often the error has come from a large/intense assembly or drawing, but I *have gotten it with a mere part file ... totally unexplained. Hence, I recommend starting over ... just think of it as more practice. 😉