Some of my geo is turning transparent as you change the camera angle exposing the underlying geo/textures? Im really stumped.. Any suggestions? Im using Maya 2011 and its happening in Viewport 2.0 and HQ Rendering.

Here are a few screen shots...

That looks quite odd.. I haven't used viewport 2 but you can get kind of similar transparency issues in the normal viewport if the alpha of the texture is accidentally connected to transparency in the material (maya sometimes does this by default if you load a texture with alpha). So if that connection exists and you don't need it then try breaking it.

Try selecting your object, go to Color>Color Set Editor and delete any color sets assigned. If you need vertex colour in your scene, make sure the alpha values are 1

Well, I tried saving my textures out without an alpha and that didnt seem to work... I went to color set editor and there are no color sets assigned either... =/ still no luck...

Are there any connections to the transparency of the material?

Yea, the funny thing is that the ones that are giving me the trouble are the ones that have transparency maps attached to them... but as you move the camera around and view the scene from different angles, the geo appears and disappears depending on what angle you are looking at it... ?? Im really confused.

Maya isn't very good at real-time transparency sorting. If you were to render the scene from an angle where the geometry seems to disappear, it would be fine in the render. It's actually pretty much the same as many game engines. Most games tend to use "alpha test" transparency (a pixel is either fully opaque or fully transparent) when sorting will be an issue. Good examples are tree foliage and hair. Alpha test sorts reliably and is cheaper to render than semi-tranparent geometry. Unfortunately you can't can't emulate it in standard Maya as far as I know. You might be able to use a CGFX shader to do it though.

For me it happens when you use a PNG as a diffuse. At times Maya will attach transparency to the material making it turn out really weird. Removing the node in the hypershade fixes it for me.

Why it shows it differently in different angles, I don't know. But when I see that I know Maya attached a transparency node again.

Pretty much what CheeseOnToast said. Also you can enable/disable poly/object transparency sorting in the modeling panel. It's iffy as to whether or not it works, for me it usually does the sorting backwards, which isn't really helpful.

Unless you need it, break the transparency connection in the material. It will render fine, and won't affect anything as far as exporters go in the end.

Yea, unfortunately Im not rendering anything out... And since it seems to be getting worse the more textures I add, makes me think that its an issue with Maya being able to handle the whole scene while in Viewport... Idk... Thanks for the help though..

There is a weird bug in Maya sometimes that causes this. Sometimes some faces become transparent. Try adding a new material Lambert and see if that makes the problem go away and then reassign the original shader. I've encountered a similar problem twice during the last month and only applying a new shader fixed it. Your problem may be different, however.

Yea, it doesnt do it if it has a lambert on it... Or if the geo behind it has a lambert on it... Its just such an odd issue...