Board Thread:Club Penguin/@comment-26431383-20150526021130/@comment-4500149-20150526023220

Here's an excerpt from a support email:

"The team is working on resolving a technical issue on our end, but some players have been successful in logging in when trying the following troubleshooting steps:
 * 1) To clear your cache, please follow the steps for your web browser located here. Once you have finished clearing your cache, please completely close your web browser to make sure all of the old files are removed.
 * 2) Restart your computer.
 * 3) Try an alternate web browser.
 * 4) Try logging in to one of the following servers: Avalanche, Alpine, Alaska, Flurry"

I hope that helps.