Z-Depth issue?

I’m having issues with z-depth. In the 3D viewport everything looks fine but when I press play I get a issue with the z-depth, as you can see in the attachment. I also had the issue in 2.49. Does anyone know my problem?

If you are not using transparency, then make sure ztransp is off in the material settings.

If you are trying to use transparency, mixing tris and quads can cause zsorting issues.

Thanks, but disabling ZTransp didn’t make any difference.

EDIT: Had to set it to opaque on the texture face panel, now it works.