Try increasing the "Performance" bars to the max if you can and see if there are any changes with those squares. Deactivating Advanced Shaders is advised too, compatibility mode for 128 MB cards should be deactivated if you have one with more MB than that.
Also make sure you got the latest graphic driver for your graphic card.
Thanks for the help, but alas, I still have square explosions and white textures.
I appreciate it, but unless there are any more ideas, I suppose I will go back to Discovery.