Windows vs. file.read

[Mike]

I have a ppm file that python 2.5 on Windows XP cannot read
completely.
Python on linux can read the file with no problem
Python on Windows can read similar files.
I've placed test code and data here:
http://www.cs.ndsu.nodak.edu/~hennebry/ppm_test.zip
Within the directory ppm_test, type
python ppm_test.py
The chunk size commentary occurs only if file.read cannot read enough
bytes.
The commentary only occurs for the last file.
Any ideas?
Any ideas that don't require getting rid of Windows?
It's not my option.