There's a new casualty in the nasty divorce between one of the "Real Housewives of Orange County" and her husband -- their house.


We've learned ... Vicki Gunvalson and her hubby, Donn, have put their Coto de Caza, CA house on the market for $2.695 million.

The reason for the divorce -- a midlife crisis, according to Vicki. 

Also, they don't get along at all.