Greetings my fellow gamers. Yes, this is the reason why it is pointless to buy more than 4GB of RAM for gaming. Games simply cannot make use of all that RAM. Its even more pointless to buy over 4GB of RAM if you are using a 32bit OS as they just cant see or use that amount of RAM without some serious editing of registry entries. There is a solution on the horizon, but its a long way off yet, might not be released until the next version of windows after Windows 7.
In the meantime, the main ways to prevent this from happening is to have a video card with a large amount of onboard ram to use for textures, SLI is another possibility. Also, consider increasing your page-file to something that is about 30GB and if you can, make sure that that page file is on a separate physical hard drive to your operating system.
For your convenience, I have located a trustworthy Large Address Enabling program. You can find the link at the end of this post. It enables 32bit programs to use up to 4GB of RAM so it should help a little. As someone posted earlier however, if it is a Memory Leak, then this will only delay its onset. Other suggestions are lowering shadow detail and texture size an see how that works out for you.
Large Address Enabler