Check the Shaders transparency node. you can do that by opening up attribute editor and looking for the tab for the shader, it'll probably be called lambert something. Check the transparency node and it is most likely set to something very low. the smooth proxie duplicates your mesh and smooths it, and turns the transparency value on your base mesh down so you can see through it. Sounds to me like you might have deleted the wrong mesh or something and ended up with the transparent base mesh. g-man