Why can't I sign in?
First try closing out your browser and restarting it.
If that doesn't work, make sure you have cookies enabled.
You can only be logged in on one computer at a time. If someone logs in using your email on another computer, you will be booted off.
The email address you sign in with is case sensitive.
If you still are having trouble signing in, try using a different browser (such as Firefox or Chrome).