I have Foldit running on an XP machine and I can login without any problems. I am using it for an EDx class on protein folding. It was downloaded from MIT for the course.
When I install it on a 64-bit Lenova Yoga 13 running under Win 8 it won't log in.
Any suggestion how to get logged in on the Win 8 machine?
You will want to post on the edx forums for issues with the edx client.
If this happens with the client you download from http://fold.it you can post a bug report in the feedback section: http://fold.it/portal/feedback
Be sure to list any errors that come up and also post your log.txt (you will find this file in the directory where you installed Foldit).