your game is corrupted because you didn't uninstall all mods before adding v1.5 or they didn't uninstall correctly.
uninstall the game, go in and manually remove any and all remaining files left on your computer including saved games and such in the documents files. then reinstall the game and it will work.
if you aren't sure there is a post explaining how to uninstall the game to clear corruptions like this
http://www.subsim.com/radioroom/showthread.php?t=133290