A change has been made that might affect different browsers differently.
We expect that everyone will be able to log in and out normally. However, if you do have difficulty logging in, here are some things you can try. Also, feel free to reply here with any details about your OS, browser, and so forth.
Checking the box for 'Remember me' might enable you to log in.
Also, clearing the cookies that your browser has for this site may help.