I've had the exact same problem and can't get to support because of this log in issue.  It is the worst on Mondays I have found and I am very frustrated that I have found that I will walk away from working with it because of the continued log in error.  Way too busy to try to log in over and over again and would really love to go back to desktop where I could just run my business and not have to trouble shoot this issue over and over again.  Very disappointed and frustrated too!!