I have this project i've been working for a while. It never gave me problems until a week or so. This is what happens: After i fro something in plant view and try to look at my model in perspective view i get like a frozen screen but only in the 3d view window. This has also happened while working in perspective view (sometimes it works sometimes it doesn't), after I modify something from my model sometimes when Rebuilding model it "crashes" again.