This doesn't appear to be a duplicate of any of the other openid questions here.  When I try to log in using my yahoo openid on any of the new sites (which worked before on stackoverflow), it seems to be working until the redirect to "http://superuser.com/users/authenticate/?token=AS..." which is just an empty page and nothing more happens after that.

Tried in FF3 and IE6, same results on meta, superuser, and serverfault.

using myopenid works.