Hi!! I've made buttercream only a billion times and never had a problem. My recipe is as follows:

250g butter

600g icing sugar

dash of milk or cream

It's always come together beautifully, and I always beat my butter for a good 5 mins before I add any icing sugar. Today it looks curdled and grainy. It's only coloured with a few drops of Americolor gel, so there's definitely not too much liquid in it. I've just put it back into my mixer with the whisk attachment to see if it gets better. I need to pipe it onto my cupcakes in the next half hour for a school fundraiser!! Any quick fixes????

AIt may be cold. While beating/whipping it in a stand mixer, use a torch to heat up the sides if the bowl.

I've figured the problem is the cream. It's not combining properly and is separating from the other ingredients. Batch number two  underway!!

ATHIS HAPPENED TO ME! I have a thread on it and everything. I put the buttercream In a plastic container and put it in the fridge over night. Brought it back out and let it sit until it was room temp. Rewhippsd it (that helped) and then added some ROOM TEMP butter (an oz) maybe and that saved it. annabakescakes suggested it.

Also sifting the sugar helped tremendously as well. If you don't do that you may want to try it

Well batch number two is done, and it's definitely much better, but still is not quite right!!! I actually think it might be too hot. It's about 30 degrees celsius here right now and about 70% humidity. Plus my oven has been on. So I've put both colours into the fridge and will leave them there until the last minute then will quickly pipe the swirls before I need to leave. I think it will be fine, but I definitely feel it's a temperature issue. 

Thanks morganchampagne - it's nice to know it's not just me!!!! I do sift my icing sugar, and I make sure my butter is well softened. I can't believe this has happened! I'm just trying to deal with it from the frame of mind that it's for a customer. It's not, and I don't have a business, but I want to one day. 

Mind you, I wouldn't leave it to the last minute for a customer. Lesson learned!!

Yep, definitely too hot. I did a test swirl on a cupcake and the frosting is barely holding up. It's all in the freezer trying to bring the temp down. I feel so incompetent! And all I usually make is BC!! 

AIt happens to all of us! We can't fight the weather lol

Ugh. I'm so disappointed. I've just taken 2 dozen cupcakes to the school and I'm not happy with them. The BC isn't holding up as well as I'd like and I know it all went wrong today because I left it to the last minute and rushed it. I had ordered some edible images and cupcake boxes from ebay about 2.5 weeks ago that should have been here for them and they didn't turn up in time. So in waiting for the postman to deliver the parcels for the day I delayed starting the cupcakes - hence the rushing. They would have been perfect had I left myself just another hour. I'm so fussy with how my cakes look, I'm still learning but I know how to pipe a swirl! Lol! Looking at my cupcakes you wouldn't think so though.

And my cupcake effort. You may as well all see my dismal failure, lol!! 

I wouldn't call it a dismal failure.  I love the colors and I bet they were delicious.  I did have this happen to me  but never figured what went wrong - Same recipe.  So if it happens again I will remember the advice from this thread :)

Thanks, that's nice of you to say. It was definitely the temperature. I think the butter was too soft to begin with and the air temp made things worse. When I piped the swirls some of them started spreading over the top of the cupcake. I made sure the cupcakes were completely cold too. I think the oil from the butter started to separate when it got too warm. It was a definite improvement when I put it in the freezer for a bit, but I would have liked to chill it completely in the fridge then remix it. I think that would have been perfect. I just didn't have time though. 

AYes that looks good!!