Here is the link:
http://forums.worldofwarcraft.com/threa ... 106626&P=1
The first post is rather long, but this is the important part that must be done to avoid yet another week of this raid bug.
So, to summarize: When starting a brand new MC/Onyxia/BWL instance, once everyone is there, before beginning or taking any action that would lock you in, have the raid leader zone out and back in. He may appear in a new instance. If he does, have the rest of the raid join him there. Congratulations, you've just avoided the unintentional raid-saving bug!
Hopefully you all can give this a shot next time you zone into a fresh MC.
Thanks