Hi,
I had the exact same problems about a week ago, and ended up building my own Pd-extended. If you want to use the package, you should install it from a terminal using something like "dpkg -i --force-depends Pd-whatever.deb" which tells dpkg to ignore the libflac7 and libquicktime0 dependencies. By ignoring these dependencies, you will be breaking a few of the extensions, mainly PiDiP, perhaps others. But you will have a working [comport]. Also, synaptic will complain about a broken database or something when you force the dependencies, so you'll want to edit your /var/lib/dpkg/status file and actually remove "libflac7" and "libquicktime0" from the list where it says "Depends:". For me, libflac7 and libquicktime0 are the only dependencies I couldn't get in the repos, so if you see any other dependency errors when you run the dpkg command, get those packages from synaptic. Hope this helps...