Thanks for the reply - the thing is that the paths etc seem to be fine and figures/environments all render well individually (or even in pairs). The problem only seems to arise when the scene hits a certain (and by no means extreme) level of complexity.

One thing you've made me think of is that I tend to customize a lot of the textures I use (to make them more realistic) and save them as photoshop files (loading them manually in the material room). Maybe P5 doesn't like handling too many .psd files at once?

Thanks again for your suggestion :)