Video Material

Okay, I got Video Materials to work in the Color or Luminance channels on my tiny macbook. Now, I'm using C4D 11 (same version) on a custom built quad core machine, and video materials aren't working. When I load the same quicktime movie into the channel, i just get a black clip of the material, and under the "animation" tab it shows frames 0 to 0 at 30fps. It used to show frames 0-1450 or however many are in there. When i try to render, it gives me a "cannot render x.mov in Material (mat)." The file size is not an issue, and wasn't before. This just started happening recently. Please help, this is very frustrating!