I've had this problem off and on for quite some time now. Upon opening certain files (doesn't seem to be any common variables between files) the Mental Ray window, within Render Settings, is blank. This has also effected the Maya Software settings window as well. I've gone online and executed a search relating to this problem but no one seems to have a fix, or explanation for that matter. This is no small annoyance. I'm currently at a standstill until I can resolve the issue. Having seen all the other posts relating to this problem i'm frankly stunned Autodesk hasn't addressed this. Is there ANYONE who has a solution. I need some help here !!!!!!!