I have 32gb of ram, plus plenty of extra page file memory, so it seems very unlikely that memory would be the issue?
You DO NOT have 32 GB, not on FSX. Since FSX is a 32 bit application, no matter how much RAM you have, it will ever, ever, use more than 4GB in theory.
In theory, because in practice, the real number is even less because, in addition to be an obsolete 32 bit application, FSX is also an obsolete DirectX 9 application ( with a somewhat buggy DX10 support ), and the way DX9 works is that, from that already limited amount of memory available, the texture memory allocated by the video card is taken AWAY from 4GB, because a copy of the textures in VRAM is placed in the main RAM so, a more typical usage is 2.6GB left and, the worse thing is: the more memory your video card has, the better chance has to steal more system memory.
One way to save *some* memory ( about 300-400MB on average ) is to switch to DirectX 10 but, that's just a temporary stopgap, because nothing can fix that absolute maximum limit of 4GB per application that all 32 bits apps suffers from.
