   PIX problem
  I've been playing around with D3D9 and came across a peculiar problem.  I was rendering a very simple test scene that was working fine, till I enabled z-buffering.  With z buffering enabled the app refused to draw anything (but the device->Clear(...) seems to go through).  I loaded up PIX to see what was going on.  Funny thing is, in PIX the render output is showing what I would expect to see.  All device states are as they should be, all render calls/resources/ect... all work/are there, depth buffer is showing accurate depth values.  In fact according to PIX it should work perfectly.I googled everything I could think of in relation to z buffers and/or PIX and found nothing useful.So my questions are, 1st is it normal for PIX output to differ from actual on-screen output?  And any ideas what could cause enabling of z buffering to cause a model not to draw (a depth stencil surface was created, EnableAutoDepthStencil in D3DPRESENT_PARAMETERS is true, D3DRS_ZENABLE set to D3DZB_TRUE, D3DRS_ZFUNC set to D3DCMP_ALWAYS, double checked all device capabilities, viewport is set).   