I am not sure if this is a major issue or simply a generic fluke but...
A thread at SEO Chat reports of a user going to MSN Search and being asked to provide evidence that he/she is an adult. The method of evidence, provide your credit card information.
Classic signs of a phishing attempt. If you see this as well, please run a spyware/adware program on your PC (I think AdAware is a good free one, but I use a Mac). I wonder if this specific phishing attempt is only targeting MSN Search users or more wide-spread then that.