So, I'm somehow sure that is a problem with your server and joomla installation.
After trying to log in frontend with my username and password I get:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, This email address is being protected from spambots. You need JavaScript enabled to view it. and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
from this url xxx/index.php?option=com_comprofiler&task=login