Okay . . . this is the 3rd time this has happened and I can't narrow it down to what exactly I'm doing wrong.
My buttercream will fall off the sides of my cake!! 
My cakes are at room temperature, as well as the buttercream. At first I thought it may be the humidity. I live on the coast of southeast Texas. But today, with temperatures outside at 50 degrees, I had my air conditioner on to keep the humidity down. But the buttercream started falling off in one little spot. 
So . . . what the heck am I doing wrong!?! 
This makes me want to quit decorating cakes!! Any suggestions are GREATLY appreciated!!
hmm... are you doing a crumb coat? perhaps if you try doing that (and pressing hard to really adhere it) with some thinned down bc, then going over it like regular it will help. Other than that, consider changing recipes. SMBC behaves totally differently from ABC.
Your icing may be too thin. The same thing was happening to me today while I was using my grass/hair tip. Try adding a little powdered sugar to your icing to thicken it up
This happened to me a couple weeks back on my coffee cup cake.. I woke up the next morning to find the entire rim of my cake down on the board... imagine my shock... it was even hardened when it fell.... I had to re-ice it and have YET to figure out what happened. The only thing I can think of is that it I didn't impress it into my crumb coat enough... maybe that is what happened with yours.. I was using tip 1M.... so it might have been putting too heavy of a coat on the small crumb coat... good luck! I also have humidity issues and I know that ISN'T what happened in my case either.
i've also found that if my buttercream has alot of air in it, it will come off the cake.
Perhaps your cake was still warm when you iced it? Alot of times you will get one hot spot, and no matter what you do, the icing just wont want to stick to that spot, even after its cooled because the heat started to break down that spot of icing. Thats my only idea, can't think of any other causes?
Thanks everyone . . . I didn't think about my buttercream being too thin. That's probably it because I tend to make a thinner buttercream. I will definitely try this with the next cake! May will be a busy month with birthdays and graduation, and I was really dreading doing another cake without knowing what I was doing wrong.
I really appreciate all your responses. This is a great website to share, encourage and support! Thanks for being there!! 
I was just browsing through this post and I am wondering what a "crumble coat" means?
I normally cover my cakes with fondant but I am planning to start using buttercream so sroadge1's experience is interesting to me.
Does this means you guys coat the cake twice to get a real smooth buttercream method?
I never do a crumb coat. I use the Wilton cake release and I get a crumb free cake good enough that I don't have to do a crumb coat. Maybe on a wedding cake I'll put a second layer on, but not on a normal basis. I think the reason your icing is coming off is because you have to actually attach it with some pressure. If you just kinda lay it on top of the other icing or the bare cake it will come off. Try applying more pressure when smoothing it on. I also use a thinner BC, unless I'm doing flowers or something that I need a thicker consistency for. I hope this helps, I would try adding more pressure before I changed the recipe that I was comfortable with using.
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