The same thing happened to me yesterday when I tried to access a search result for Rhode Island State census. I used other databases all day long, but encountered the "welcome to ancestry, please log in" in the Search Result box.
My experience was a bit worse than yours, however. After I logged in, I encountered the same screen again - it was kind of in its own circular loop. Log in - welcome - log in - welcome.
This was a relatively minor record, but the records you mention are major resources.