Invalid Cert (Yahoo)

I am trying to log into my yahoo account and I am getting an invalid certificate error. I know this can mean a phishing site, but I logged into my wife's macbook air (from work) and got the same error message. Could this be an issue with the browser. I am a new mac user and don't know much about the ins/outs of Safari yet.

Try a different browser and see if the same thing is happening.

I use just Safari since the release of Lion and while Yahoo! does not use encryption (https), I can access my Yahoo! mail with no problem or certificate error. I use Google DNS (8.8.8.8 & 8.8.4.4) as my primary and secondary DNS before using the DNS from my ISP.

I do have Safari checked to notify me about fraudulent websites, located under Safari -> Preferences -> Security. I do not use any proxy settings or a connection script; Safari -> Preferences -> Advanced -> Proxies: Change Settings.

Have you tried clearing out all website data and then accessing Yahoo! again? Safari -> Preferences -> Privacy -> Cookies and other Website data: Remove All Website Data...