Buffer has not the same options?

Hi... I have a problem with my flightsim. In fullscreen-mode, many edges begin to "flash". It looks like a ZBuffer-problem. In window-mode, everything is okay. This is the code: CreateWindowEx(dwExStyle, "OpenGL", // Klassenname "FH-FlighSim V0.2 )", // Fenstertitel dwStyle | // Window Style WS_CLIPSIBLINGS | // Required Window Style WS_CLIPCHILDREN, // Required Window Style 0, 0, // Fensterposition WindowRect.right-WindowRect.left, // Fensterbreite WindowRect.bottom-WindowRect.top, // Fensterhöhe NULL, // Kein Parent-Window NULL, // Kein Menü s_hInstance, // Instanz NULL))) // Nichts an WM_CREATE übergeben static PIXELFORMATDESCRIPTOR pfd = { sizeof(PIXELFORMATDESCRIPTOR), 1, // Version PFD_DRAW_TO_WINDOW | // Window-Unterstützung PFD_SUPPORT_OPENGL | // OpenGL-Unterstützung PFD_DOUBLEBUFFER, // Double Buffering-Unterstützung PFD_TYPE_RGBA, // RGBA-Format gewünscht g_Config.colorDepth, // Farbtiefe 0, 0, 0, 0, 0, 0, // Farbbits ignorieren 0, // Kein Alpha Buffer 0, // Shift Bit ignorieren 0, // Kein Accumulation Buffer benutzen 0, 0, 0, 0, // Accumulation Bits ignorieren g_Config.zBufferDepth, // Z-Buffer 0, // Kein Stencil Buffer 0, // Kein Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserviert 0, 0, 0 // Layer Masks ignorieren }; Normally, I use a 24Bit or 32Bit-ZBuffer, the colordepth is 32Bit. The resolution is 1280*960 or 1152*864. Why the hell does this problem only exist in fullscreen-mode. It the same code... Now, I noticed, that the there is a differenze between the images from the frame and from the buffer. If I have 80fps, the edges are flashing 40times per second. If I have 40fps, the edges are flashing 20times per second..... Is it possible, that the buffer has a different ZBuffer-depth? Thanks...