I made it ahead last night and was wonderful - kept in fridge overnight.
Let stand out for an hour on the counter when I got home from work and put some in bowl to rewhip to start decorating cakes and IT TURNED INTO A MESS!!!!
HELP ME PLEASE!
I have to do 2 cakes tonight and no more time or ingredients to make more. What did I do wrong? This has never happened to me, I am frieking out, PLEASE HELP ME ASAP!?!???

and please note that I did do a search and nothing came up with SMBC and separating in the search.
I dont know what else to search and DO NOT have the time.
Thanks!

BUMP

Come on, are you KIDDING ME????
BUMP BUMP BUMP

OK- I think what happened is that the buttercream was still cold when you whipped it. It has to be at room temperature or else it will break/separate (this is what I read in the cake bible). I usually defrost mine in the microwave (only 10-20 seconds at a time on lower power b/c you don't want to melt it!) if you're in a hurry and don't have the time to wait for it to come to room temp on its own.

The problem is I've never had that problem so I don't know how to fix it. I'm sorry to say but it may be unfixable. Although I believe you can add it to a new batch of buttercream and it will fix itself (so at least you don't have to toss all those expensive ingredients) But again, I'm not sure, this is just what I've read in some books.

Ok, I went back to it as I didnt get reply for a while and just beat the daylights out of it.
Luckily it did come together again, but it took about 10 minutes.
Thanks.

Phew, I'm glad it came back for you! If I'd seen this post sooner I would have told you to do exactly what you'd done. It's usually pretty easy to repair this stuff if temperature is the only problem. If it's too cold I actually warm the bowl with my hands while I'm beating the icing (I'll even run my hands under hot water to reheat them). If it ever happens to you in reverse (i.e. too warm) get a bag of frozen peas/etc and hold that around the bowl while beating it.