What are your computer specs, are you running FSX SP2 and what are your FSX settings for traffic and graphics? Did you apply the modification to increase your virtual address space? If you don't know what I am talking about, I suggest you go to AVSIM and search the FSX forum for "Out Of Memory." There is one message entitled "OOM Error explained in comprehensible English" I'm not sure it is totally comprehensible, but you should get the idea. This is a very common error message and you probably need to do what it says -- reduce your settings.