I am adding a new mimetype for mp4 files to Tridion. I have followed the instructions on the [Tridion Live Content site here][1]. (login first). And I have confirmed my settings match the [blog post here.][2] And then I flushed my browser cache and even restarted the CMS server. But, I still get the following error: > The file extension of the selected item is unknown. The specified file > does not match a supported Multimedia Type. Any ideas? [1]: http://sdllivecontent.sdl.com/LiveContent/content/en-US/SDL_Tridion_2011_SPONE/task_F8456F78DAC540F2A72BC8EC70E2CA4C [2]: http://alokbhatt11.blogspot.be/2013/06/upload-mp4-videos-in-to-tridion-cms.html