zsfritz said:
I can't solve the same problem in my side.
I would like to play a mp4 file h264 with mediaelement but I can't. I get a mediafailed message -  c00b11d1.
Anyway I can play it with Windows Media Player - i have K-Light codec pack installed.
I use a Vista x64 ultimate - but I tried to use the application on a x86 XP.
Anyway I can play wmf files with my player withour any problem...

Does anybody can help me?
This is probably too late but I think I know what the issue was. You are probably compiling your app from "Any CPU" (check the Platform target Build tab of the project properties.). This means that on x64 systems the media element will be attaching to the 64bit version of the player runtime. The reason your results are mixed is that you don't have 64bit direct show filters installed for the files you are trying to play. Because 64bit directshow filters are quite hard to get right now Windows Media Player runs as a 32bit process even on x64 systems.

As a work around change the "Target platform" to x86 and you'll probably find your problem disappears. I had this exact same issue when I was testing out the Media Element.