Internet Explorer 7 - Cannot Access New Yahoo Mail?

I am running Vista Home Premium w/Internet Explorer 7.0.6000.16609 (yes, they are legal full edition retail). I have always been able to switch back and forth between Yahoo! Mail Clic and Yahoo! Mail Beta. However, when Yahoo implemented these new changes within the past 6 hours, I have been unable to access New Yahoo! Mail (formerly Yahoo! Mail Beta). When I try to access the New Yahoo! Mail, I am redirected to a page informing me that I am currently using a Beta version of Internet Explorer 7 (which I am not) and then instructing me to either upgrade to a compatible Internet Explorer 7 or to return to Yahoo! Mail Clic. So, after several retries and cleaning my browser temps, cache, cookies, etc... , in exasperation I followed the upgrade link to Microsoft to attempt to "upgrade". MS tells me that I have the most current version of Internet Explorer 7. Any suggestions on how to solve this. I can access New Yahoo! Mail with Opera and Firefox, but I prefer Internet Explorer.