Apache returns truncated image (cross posted on serverfault.com)

Question

I am bringing up an image directly through firefox (no PHP or other scripting code) and it appears that Apache is returning either a truncated image or a corrupted image.

I get the top 5-10% of the image. It appears that I get complete width and height info.

If I hit "refresh" (in firefox) I get about 5 more lines of the image. And if I hit refresh again I get another 5 lines.

In IE I get the same initial 5-10% of the top of the file. But refresh does not give me any more.

Bringing the image up across the network through a mapped-drive reveals the entire image. (so the image(s) itself seems to be okay).

(If I point firefox to the image via mapped-drive rather than through Apache firefox brings the image up just fine. So it does seem to be Apache at issue)

Any ideas?