http://bugs.winehq.org/show_bug.cgi?id=20335
--- Comment #3 from Austin English austinenglish@gmail.com 2010-08-16 23:18:32 --- (In reply to comment #1)
It sounds like it's hashing padding bytes. Probably should be reported to the X.org folks.
X.org bug filed: https://bugs.freedesktop.org/show_bug.cgi?id=29600