Have you already tried to choose a different resolution or changed other graphics options using the configuration tool config.exe (in the Gray Matter installation folder)?
If not - I suggest to try this first. Maybe you're using a different graphics card, display or just graphics drivers now and the old settings don't work anymore.
If that doesn't work have a look at the tools/programs that are running in background and try to run the game with as few tools/programs in background as possible. There are several types of tools that can interfere with game graphics. Like for example video/screenshot capture tools, graphic card specific tools (settings, overclock, monitoring tools), tools using overlay (e.g. tools that let you play games in fullscreen and chat via graphics overlay at the same time). Sometimes even tools you don't think of like download managers. So disabling as many tools running in the backgroung before starting Gray Matter might help.
If you have ever connected a second display at the system this might also a problem. In that case make sure that no second display (even if not active) is set in the graphic drivers display section.
