Yeah I'm having this problem too. I noticed it started soon after midnight after the day being reset. I couldn't log in and got the server busy error. I tried again about 4 hours later and the page wouldn't load at all and I got a generic web search page. I just tried again now (7am PDT) going straight to the Cartoon Network site and I'm back at the generic search page.
My guess is that since it's Monday, they are working on the next update/additions to the game. Cartoon Network usually does their updating on Mondays to their sites. I know they did that like clockwork with Orbit, when that was around.
Stay patient and keep checking back. I'm sure once they get the additions into the game it will be back up and running just fine in no time.
~Vicks