Since few days I am experiencing this issue. I was logged in to Twitter with my primary twitter account @debiprasad on Firefox and I had selected to remember that log in. I decided to use Twitter with my primary account on Chrome and use another Twitter account on Firefox. So, I signed out, and signed in with my other username. I selected the option to remember this login (with the new account). I don’t remember exactly, but I think there was no problem for first few days. One day, when I opened Twitter on Firefox, I saw I am automatically logged in as @debiprasad. I tried to sign out, so that I can sign in with my other account. But after page loads, I found that I am again logged in as @debiprasad. Again I tried to sign out and finally it showed me home page (when no one is signed in). Then I able to sign in with my other username, with “remember me” selected.