Downloaded AUTOCAD for MAC 2013 free student version. Installed, tried to enter provided serial key and it said invalid code. read about the workaround and installed again, selecting the 30 day trial option in standalone mode. When i tried to open auto cad, the opening screen is displayed, then closes. Never even see the program. I have installed, deleted, and reinstalled auto cad for mac 2013 several times, as well as for 2012 and 2011. When i delete, i uninstall using the provided uninstaller, as well as manually deleting the residual files in the Library-->autodesk, Llbrary-->application support--> autodesk, and Applications--> autodesk. None of the provided "support" resources on Autodesk's site appear to provide any hint of a solution to my problem and, conveniently enough, i can't find a single number for an actuall customer service person. If anyone has ANY HINTS at how i might be able to solve this problem and OPEN THE PROGRAM, i would greatly appreciate it! Thanks.