I've never had this happen but here's a bump. Anybody familiar with this problem?
I think it depends on what kind of crack you have first of all. If you let the icing crust too long, and then try to smooth it witht the Viva, you get tiny cracks in the icing.
One of the other crack issues is if you don't have enough support for the cake, you get those big cracks in it.
I had a new situation the other day....I made a cake with a dark John Deere green color to it, and I didn't let it set for very long before doing the viva - and there were a couple of areas that got the small cracks in it - I think it was actually from the coloring (??) Never had that happen before.
Is this happening when you move the cake? I used to get cracks in my cakes when I used cardboard cake boards. I've switched to plywood and it's eliminated this problem.
I had that same cracking problem with a cake I made this past weekend. It seem to happen when I would lift the cake on the cardboard, and it made it bend. I was putting the cake in the box when my friend got to my house and it started cracking, I was so embaressed. Luckily, they loved it anyway and thought it tasted great! Originally I thought it may have happened because I had previously frozen the cake before I decorated it (first time I had done that).
Sammy,
Does it get costly using plywood? Sounds like a good idea but I don't know if I can afford that or not, I hate to go up on my cake prices. 
Connie
This happens to me unless I use a VERY sturdy board/method of support underneath.
If your icing is crusting before you can finish smoothing with the Viva, try adding a little more fat to your recipe. Also, icing crusts slower on a chilled cake (condensation). If your cake is big and you don't think you'll be able to hit every inch of it with Viva before it starts to crust, pop it in the frig for about 20 minutes before you ice it. Don't let it completely chill otherwise it will take FOREVER for the icing to crust.
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