First of all, I'm aware this question belongs to meta, but I can't log in there.
The problem I've had is the following:
I used to log in to SO sites with myvidoo provider. This provider is not supported anymore. I luckily had a cookie on my browser, which made me remain logged in to Stack Overflow, and I was able to switch Open Id providers. But even though I have my accounts on ServerFault, Meta and SuperUser related to this one, I can't login on those sites. I didn't have time to swap openid providers there, so I've been locked out.
What can I do?