Since you're getting an error I personally added (:P), I know that you're using a more recent snapshot (168 or newer). Next time when reporting an issue, please tell us which version of TPT you're using on what operating system and, if the error seems to be HTTP-related, whether you use a proxy or not.
That error basically means that TPT fails to encrypt its connection to powdertoy.co.uk, which can happen for a variety of reasons. It should normally only happen if the certificate on the server expires or similar, but seeing as nobody else is reporting the issue, that's probably not the case here. See the questions above.
Try logging out from the game and then logging back in.
I got this error too.
Yeah.
Sorry for not responding! I've tried the log out and log in metod, but i can't login into my account (in the Powder Toy application). Im using the latest version, updates install with no problems.