Last week we updated the Autodesk Feedback Community where over 50,000 people participate in Autodesk Beta, pre-release projects, and some future research projects with customers. In the minor update, it required a few people to delete their temporary website browser cache. I am not certain why this occurred, and am investigating it and to see if we can prevent from occurring in the future. If you were affected below is the solution and I do apologize for the pain.
Symptom: You may see the login screen overlaid on the main home screen.
Solution: Delete your browser cache to remove the cached version of the old web page. Some browsers cache a web page to gain better performance the next time they load the website in the browser, but when the website changes it can cause weirdness to occur as the old and new website components mix.
When I seen this on one machine in Internet Explorer 9, I went to Internet Options > Delete Browsing History
How to delete browser cache in other browsers:
Delete your cache and other browser data
Good article on clearing browser cache:
How to Clear Your Browser's Cache (with screenshots) - wikiHow