Seems different browsers have different problems here. I only use chrome.
Could the mobile device be autocorrecting your password to an incorrect password? My previous phone use to do that.
Hey, we're aware of the issue and have created a thread regarding it, please report your mobile sign in issues here - http://gamrconnect.vgchartz.com/thread.php?id=232909 so that Talon can hopefully narrow down what exactly the issue is.