I found some transparent shape on my skin after i updated the version 0.7...
And i remember I met a similar bug once. So if it's impossible to make these hollow out really fixed, please try to add a "lining" inside the layer which should place skin.
btw, i'm using an ATI GPU. this bug also have a possibility to be happened because of the ATI's drivers.
sry for my nearly chinglish.lol.