For all those who asked, libupnp 1.6.6 is needed because every other version before that has bugs. We need no bugs around, do we? If your distro has not updated it, please ask them to, there is no reason not to do it.
As a temporary workaround, amule tarball includes a script called "amule_build_install.sh" that shows exactly what you need to do if you decide to compile anything by hand.
Cheers!