Virtual memory uses hard disk space so it is important to keep the hard disk specified open for virtual memories use. Always optimize your symbol sets when you are making them and before you start defining classes. Optimizing your symbol sets reduces their size and therefore decreases memory requirements. It is absolutely essential if you are working with large numbers of terrain or unit symbols or if you delete any symbols while making the set. Consider upgrading to Windows 98 SE, if you are not already running it.
Applications frequently leave large chunks of memory unavailable even after they are closed.
These fix that problem quickly and will make all your programs run better. Consider installing additional memory. Plus all your other applications will run better too. If that doesn't work, check the section on Graphics problems in the symbol corruption section . Make sure you have the most current version of your video card driver.