That sounds more like a graphics card problem, OR it could be your screen resolution. Try updating your driver as stated by Omanes, or if that doesn't work, set the screen resolution (in RTW's video options) to a higher setting and to a 32 bit depth. E.g. 1280x1024 for a 17" standard (not widescreen) monitor, or 1024x768 for a 15" etc. Set it to it's highest resolution possible.