A tiling pattern shows up in the preview
This can be a result of an out-dated video driver. You will want to double check your video card manufacturer in the Device Manager and then go directly to their site to download and install the latest video driver. An example would be if you have an EVGA 7200GS 256MB PCI-E video card. EVGA is using an Nvidia chipset, so you would want to go to the Nvidia website to get the latest driver available.