I wonder if we might somewhere be opening a file in text mode? That would
certainly give us a windows-specific bug like this.  I had thought that we had
expunged all of those, but if we can't find this bug anywhere else, a review of
that possibility might be in order.

Actually, Zooko, could you post a link to the logo.png file that exists in the
working directory after this failure? Also, a quick look to see whether it's a
valid png file would be instructive.  If it's been corrupted by the addition of
extra '\r', we ought to be able to recognize this just by looking at the file
that's left over.

David