When logging in to answers, logins are against my.atlassian.com. M.A.C. authenticates an upper or lower case login successfully, and returns a success message. However, answers is not case sensitive, and is not recognizing this user.

This was reported in a different way at:
https://answers.atlassian.com/questions/4762/problem-logging-into-answers-atlassian-com-with-safari-on-an-iphone4