This is usually a result of either a missing or mismatched CSRF token. If you haven't placed a token in your form, do so by echoing the function 'Form::token()' somewhere inside your form. Otherwise I believe this is handled for you if you use the 'Form::open()' syntax to open your form. You can learn more about it here: http://laravel.com/docs/html#csrf-protection
The token is stored as part of the user's session, btw, so it's possible you can get a token mismatch error if you store your sessions in the database, then wipe the database in between getting a form and posting it.
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