Can't change graphics settings

As the title implies, I cannot change my Garrysmod graphics settings, bar resolution, or else GMod crashes. I could set all settings to highest before, now I can’t. I’ve cleaned my GMod, defragged the game, verified the files, and still no avail. Any help here?

Have you tried an uninstall?

No, and to be entirely frank, I don’t want to do that. I want to see if there are any other ways that will be quicker.

Make sure your command line is cleared, it tends to interfere with the settings.

That looks like it’s done it. Much obliged.