https://img508.imageshack.us/my.php?image=mayaxh4.jpg

The picture I suppose shows everything, but let me explain to make it clearer. The sphere is with an ordinary Blinn and even more ordinary Checker texture, the cylinder is with a Lambert and Cloth texture, the cone is with a Phong and fractal texture, and the cube is with an empty Ramp Shader. When i press 6 to show the textures in the Viewport the effect is like on the picture above, but when rendering everything comes up normal (upper right angle on the screenshot). Maya is version 8.5, and my PC is: Pentium 4 3GHz HT, 2GB DDR and nVidia GeForce 7900 GS with the latest drivers from the nVidia website. The problem is from quite a long time, but since I am learning modeling and using High Quality Rendering in the Viewport, but when the scene is more complicated it’s difficult because it gets choppy.
I think that the problem was from one of the drivers for the graphics card, but I’m not sure, and nVidia didn’t help at all… Any ideas?