Organized here by their common nicknames, here are some error messages you may see in Skyrates and possible troubleshooting steps. In almost every case, clearing your browser's cache, waiting a few minutes and reloading the Flash client usually helps.
When the loading bar gets "stuck" about 1/3 of the way through, you've been "1/3'ed". The Skyrates server is up, but it's not accepting your login credentials (to log you into the Flash client) or is unable to accept them. It usually rights itself within about 5 minutes, but if you're unable to login after that long, make a post about it in the Bug Reports section of the Skyrates Forum.
This one usually indicates that the Skyrates server has gone down or that you've lost your connection to it. Follow the moose's advice: try again (but you usually don't have to wait more than 1 minute).