strange colors

when I use 24 or 32bit color mode the colors look strange… in 24bit mode I only see the lightning colors the places who is darker are black! and when I use 32bit color mode then I got some strange stripes instead of nice softed side of a cube! is this becouse of my hardware ? I have ATI Rage Pro 3D and a Voodoo 2 12Mb ??

perhaps the use of int instead of float/double somewhere in the code?