Page faults affect performance, but there's no relation between page faults and stability. They're only "bad" if they're unnecessary. Sometimes they're just unavoidable. 3D rendering usually requires a LOT of memory for geometry information and especially texture data. It's typically accessed in an irregular pattern -- which means that if you don't have enough "working set" (the physical RAM pages each application is currently allowed to use) it'll have to constantly move the data between RAM (working set) and disk (backing store).

That can really slow things down, since disk access is lots slower than main memory. Still, if that affects stability, then the stability in question is the OS, not the application. (Page faults aren't controlled by or even normally visible to the application.)

I notice that the display up in the first note shows the system has allocated about half of the system's 1Gb RAM. With any moderately complicated scene I'll bet Poser could easily use that much all by itself. Which also implies you might have had plenty if the system had allowed Poser to use the other half gigabyte.