Users cant login in mobile

I want to enable colaborators, editors, etc. be able to login to post in my site using his mobile, but when they go to login screen, they cant login, the page just keeping asking and asking username and password. If they refresh page, they still not logged…

Im using WordPress Mobile Pack plugin, but even if I disable it, they still can’t log in. I think probably is an error in wp-login.php, but my knowledge of php isnt so high…

Can someone help me?

PD: my page is: http://www.musicformice.com/wordpress