Seems like it's caused by cbf50e333dc1e80cd968c5ee931b4d6886b116a4 http://www.unicode.org/versions/Unicode6.0.0/UnicodeStandard-6.0.zip
Fixed in: commit 684cd3ebbbeaffbf416a09aad6af2cb160cec6bb Author: Robin Watts <Robin.Watts@artifex.com> Date: Fri Jul 29 14:22:29 2011 +0100 Bug 692382: Fix typo that broke encryption support. Not quite sure how this one slipped through - must add encrypted documents to the mupdf test suite. Thanks.