As some users have noticed, newer versions of numpy are incompatible with one of the main dependencies for pyMDmix installation: Biskit. Biskit uses an older version of numpy (Numeric, or oldnumeric in the code) that is currently obsolete and not supported anymore. Because of that, installation of pyMDmix fails!
But don´t worry, I solved the issue by updating Biskit sourcecode to use standard and well supported numpy functions and installation runs smoothly as it was before. However, to use the updated Biskit version, the code should only be installed using SVN and checking out the trunk source code at sourceforge:
All other means of installation (automatic installation using pymdmix installer, easy_install, pip, or even the ZIP file in sourceforge) will install the previous non-updated version of Biskit. I am working with Raik, the main developer, to update all these other files and means of installation. I will post a new comment as soon as they are working and available.
Sorry for the inconveniences and enjoy the program again!