I have checked this with my still currently installed Audition CS6 and I don't get this problem at all:
So it started when I tried to import a video into a multitrack session from a newly installed Audition CC—installed just after Premiere CC. It came up with an error and told me to enable "DLMS Format Support". So I do that, then restart. Now it imports, but the audio freaks out and I get an error saying "an error was encountered during the conforming process: unable to read or decode the file". Okay fair enough Audition, what format do you prefer? Oh I see, you like .mov and .mp4, so I try ProRes and H.264 at 720p 24fps / 48kz 16bit stereo and both files do the same damn thing. Restart etc. no difference.
So I think to myself, screw the audio. I go and create just a video file without audio. After Audition finishes spinning it's beach ball around it seems to have loaded the video file onto the video track. Oh, but wait, it's just all black.
Just to reiterate: All these formats are supposedly supported and Audition CS6 doesn't have any issues with any of the video files.
Any ideas?
Cheers.