I doubt there's anything I can do about this, but I'm wondering what I did for next time.  I made a camo smash cake...it looked perfect last night.  But this morning, it seems very hard.  I wouldn't normally worry too much but since it's a smash cake, I want my little guy to really get into it, you know?  

I used Sharon Zambito's recipe, which is the one I usually use.  Man.  I hope it doesn't suck.  :-(

Add about 3 Tablespoons of Glycerin to your next batch of icing. I buy it by the gallon. If you don't have a wholesale source. You can order much cheaper through any pharmacy rather than Wilton.

Less sugar or more fat.  You can add corn syrup but it's really not necessary and adds to the sweetness.  I would reduce the sugar personally.

Awesome, thank you!!  I ended up making a new batch of icing and re-icing.  I would feel so horrible if it just crumbled into a big mess.  I am keeping my fingers crossed that I just messed up that batch of icing.  I will know next time!