After upgrading Lion to Mountain Lion, the MacPorts system seems broken.
Refering to the MacPorts's migration page, the best solution seems to unistall all and reinstall all the ports.
Is there a simpler/less drastic solution?
Here is how I fix it (after Mountain Lion update):
After that, everything works except MongoDB, After some research, I found this article (How to upgrade MacPorts to OS X 10.8 Mountain Lion) by Phil Freo.
Thanks to this article, which reassured me in my approach, I also found the solution to my last issue: