I find that dpkg seems to work OK (fortunately). But something's definitely wrong, and I'm guessing it's due to the libc6 upgrade. For example, oggenc (from vorbis-tools, last changed months ago) doesn't work---it always produces a file with an average bit rate of 0.7 bits per second. The file seems OK---ogginfo reports sensible looking data from it---but the bitrate is entirely wrong.