My butter cream icing seemed to melt off the last two cakes I have done... it hasn't been that warm in my house.... I use an all butter ABC... if I use a part Crisco will that help it to be more stable?
I would also like to know. I have never had this happen to me but if it does I would like to know how to fix it. Sometimes i have problems with my shortening based butterecream sticking to the cake but it's because the sugar/shortening ratio is off. just add a little water and that makes it sticky again. sorry i'm no help but maybe my comment can bump it up
All butter recipes will become soft and not stable faster than a recipe using shortening. The recipe I use has 1 1/2 cups shortening and 1/2 cup salted butter. Don't use Crisco go out and find either Hi ratio shortening or a store brand such as Walmart. Liquids don't mix well in Crisco making colors separate and leaving a grease slick on the roof of your mouth.
I too had a terrible problem with my standard Crisco based buttercream for a cake class I conducted. When I got home I remembered that when the Crisco people changed their recipe to all vegetable based so many people complained and demanded a "fix" so they suggested adding a heaping tablespoon full of white flour to each batch. It does help. Crisco just isn't working for decorators anymore, need to get high ratio icing instead.