Soup! My buttercream has turned ed into soup

I've managed to end up with a giant bowl of butter soup. Help! My whites were solid, my buttercream was good. But somehow mixing them together has turned it all into a giant liquid mess. In an attempt to stiffen it up more I continued whipping but it hasn't done much. The consistwncy is pretty strange to be honest. Will it maybe set overnight? What a mess... thanks