Hi Vitor,
I suspect this is related to the recent re-implementation of all U-Pb math-related functions as a python module so that users can see how they're implemented and change it if they want something different. When running the latest version for the first time, you should have seen a dialog that asked you where you wanted to store iolite's reference materials and python stuff. Within that path there is a site-packages folder that contains iolite_helpers.py. If that path/file isn't being found by the built-in python interpreter then the concordia/discordia stuff will fail.
A few things you can do to help us diagnose what went wrong:
1) What of relevance is output in the python console and in iolite's messages?
2) Report the output of python’s sys.path, e.g.
import sys
print(sys.path)
which you could run in the python workspace or console.
Many thanks,