I have trainz 2010 and I am having the same problem. I am not familiar with 2012 but i was told in '10 to go to the content manager, 'file' and click on extended database repair and let it run (without using the pc) this has not helped my case so far but maybe it can help you.
Right-click on the desktop icon and Run as Administrator. I got that message too. When it opens, go Options, and make sure Fullscreen is ticked, and you select shadows to be on or off via the different tags.
:'( :mop: :'( :mop: