VideoReader and all other video reading functions are broken on my Mac. Ideas?

Whenever I try to read a video file (such as a .mp4, .mov, etc) using the VideoReader object on my mac's install of Matlab (OS 10.7.4, Matlab 2012a, also errored in 2011b) I get an error like

>>vr = VideoReader(filename)

Error using VideoReader/init (line 447) The file does not appear to have any video or audio data.

These media files play fine in Quicktime, VLC, etc., and this error is not the file not found error of specifying the wrong file name. It has done this for every format and encoding method I've tried, which are numerous.

Does anyone have an idea what might be wrong with my install?

Thanks.