I have AutoCAD LT 2013 on my Mac. It has all the sudden started shutting down any existing file I try to open. It opens it for a second then shuts AutoCAD down. It has never done this before. I looked for updates and it shows there is one for my version, I try to install it and it says I am not running a new enough software on my Mac. I have the newest software out there. How do I fix this? I am not tech saavy and need help. I have called Autodesk and their customer service is nonexistent. HELP!

Ashley