Depth Buffer issues

Im having a patch with multiple renderers. when ever I change the depth buffer format to D16 or d24x8 the mesh object disappears, I try to clear the depthbuffer, and then it shines at me for a split of a sec. all the other formats (lockables) work well…
why is that? should I be changing to the same format on all renderers?
I have a Radeon 5700 and its a bootcamp machine///
I hope I make sense =,

Thank you all

can you do screenshot of render transform pins
hard to tell without that…