So you're using the GNUnet team PPA, and not official Ubuntu packages. That would have been an important information to give us... I assume you're using Intrepid. You've just installed gnunet for the first time?
I think there's something broken since a few days because of the new version 0.8.0c-0-0ubuntu0~ppa0. It should depend on libmicrohttpd, not libmicrohttpd4. For now, you can install the version 0.8.0b using Synaptic, menu Package -> Force version.
Markus: Do you think the only problem is with libmicrohttpd versioning? I can't find it in original Debian packages, that's strange.
So you're using the GNUnet team PPA, and not official Ubuntu packages. That would have been an important information to give us... I assume you're using Intrepid. You've just installed gnunet for the first time?
I think there's something broken since a few days because of the new version 0.8.0c- 0-0ubuntu0~ ppa0. It should depend on libmicrohttpd, not libmicrohttpd4. For now, you can install the version 0.8.0b using Synaptic, menu Package -> Force version.
Markus: Do you think the only problem is with libmicrohttpd versioning? I can't find it in original Debian packages, that's strange.