I have just received the following email:

We are aware that the Yahoo! Groups site was intermittently unavailable for a few hours on Saturday morning and again for approximately one hour this morning. As a result of this downtime, some accounts have been temporarily disabled by being put into auto-responder status. We are currently working on re-enabling those accounts.

We appreciate your patience and apologize for any inconvenience. Our engineering team is working to get this issue fully resolved as quickly as possible. We'll post updates as they are available. 

Regards,
Jami Heldt
Groups Community Manager

I do hope that the engineering team will resolve these problems speedily.

Sue