My test messages were, indeed, taking a long time to load and eventually did, but I never got an error message. ???
I guess that's why they call it beta. I know you don't, but other people (referring to myself) usually forget that a beta is almost expected to have bugs. So many complaints -- or at least they seem like complaints, not 'bug reports' -- at the Yahoo feedback site, etc.
Thanks for the warning, though, about this email loading situation !