It is not a problem at all to run it on two versions of X-Plane. This is completely within your right. The problem you are likely facing is memory exhaustion. We have seen this a number of times across various products now with X-Plane 10. It's a very hefty 32-bit application and some systems just aren't cutting it any longer without the 64-bit functionality. Basically, X-Plane will shut down functions or plug-ins in an effort to keep itself running. You may want to try lowering the resolution of your textures in X-Plane. Try setting it to "low" in the X-Plane resolution settings menu. If this does not work, re-name your Custom Scenery folder to 'Custom Scenery_old', and create a new, empty folder titled 'Custom Scenery'. Just for our information, can you please also list the system specs for the machine this is running on?