Hmm... an additional problem with vnc4 is that it doesn't build on edgy (or feisty), it seems. Were you able to build and test your debdiff on edgy? Perhaps the best approach would be to fix the build in feisty first, and then figure out what's needed to make it build edgy from there:
dpkg-checkbuilddeps: Unmet build dependencies: mesa-swrast-source (>> 6.4.1) -- vnc4 authentication bypass https://launchpad.net/bugs/77383 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
