Rapidshare have implemented a new captcha for some time that asks the user to enter four out of x letters that have a cat (others have a similar looking picture of a dog with a smaller head) in the background. This new captcha is confusing to users and many have decided that it is not worth the trouble.
Solution? Download HappyChecker 1.0 for Rapidshare Happy Hours Notifier
{via ghacks.net}