The bug looks fixed in marionnet_0.90.6+bzr508.orig.tar.gz. Though I have not actually tested this version, only checked the source tarball.
https://deb.debian.org/debian/pool/main/m/marionnet/marionnet_0.90.6+bzr457.orig.tar.gz/usr/share/marionnet/images/launcher-icons/marionnet-launcher.png is corrupted for me and some people on #debian IRC. The one in marionnet_0.90.6+bzr508.orig.tar.gz works fine. After applying the fix I suggested earlier (optipng), the program starts but displays a bunch of other error messages and UI items are missing. At this point I'll assume it's unusable for me on stable, I'll wait for the next release.
