AE CS 5.5 Mac OS 10.7, Imported screen captured .mov file is low quality

Question

    Hello
  I'm importing a few screen grabs that I made using Snapz Pro video. The quality of the original file is great. But when I import it into AE CS 5.5, and then zoom in and animate it, it looks really, really bad ONLY when I render at 1/2 resolution.
  If I did the same thing to images, they would look fine. But this movie asset (h264) looks horrible unless it's rendered at exactly 100%.
  To be clear, this only happens at render, and in the preview pane when the pane or render are set to less than 100%. If I view or render at 100%, it looks fine.

Answer 1

Seriously?!?!
What version of After Effects? Include the minor version number (e.g., After Effects CS5.5 with the 10.5.1 update).
10.5.1
Have you installed the recent updates? (If not, you should. They fix a lot of problems.)
Yes
What operating system? This should include specific minor version numbers, like "Mac OSX v10.6.8"---not just "Mac".
Os X 10.7.3
What kind(s) of source footage? When telling about your source footage, tell us about the codecs, not just the container types. For example, "H.264 in a .mov container", not just "QuickTime".
H264 .mov captured with Snapz Pro Video
If you are getting error message(s), what is the full text of the error message(s)?
None
What were you doing when the problem occurred?
Rendering at half resolution, or previewing at half-resolution (also happens at other resolutiosn below 100%)
Has this ever worked before?
Huh?
What other software are you running?
Chrome
Do you have any third-party effects or codecs installed?
Surprisingly, no.
Tell us about your computer hardware. Include CPU type and number of processor cores, amount of RAM installed, GPU, number of disk drives, and how any external drives are connected.
Mac Pro 12-core 2.93, 24GB RAM, Radeon HD 5870, 4 internal drives (7TB total), about 10 external drives (RAID and separate other drives)
Do you have any third-party I/O hardware (e.g., AJA, Matrox, Blackmagic, MOTU)?
No
Are you using OpenGL features in After Effects?
Yes
Does the problem only happen with your final output, RAM preview, or both?
Both
Are you using Render Multiple Frames Simultaneously multiprocessing?
Yes