Read your post and had my own ideas of what you could try differently. By the time I got to the end...Iron Baker, The Casual Kitchen and Antonia had stolen everything I wanted to say!!!
What happened to you sounds exactly like what happened to me when I tried to make a Tres Leche cake. The 'leche' part came out like ummm...sorry for those with week stomachs....vomit. Flavor was lovely, texture could not have been worse.
I learned after that you have to have your bowl and beaters chilled, and you should whip on the lowest speed possible. This should allow it to whip up nice and fast and not curdle.
I'm glad to know if I do that with ganache, I can re-melt. I don't think there was a solution for my Tres Leche, so we just ate it at home