I can't really say I have had "problems" per say; occationaly it has fits opening the material lab but that seems to only happen if the texture file is located on C: (I have P4/P5 on D:) - aside from that it has actually shown me some improved performance such as not locking up Windoze when closing the app, even after several renderings (yes RayTrace is slower, but hey 'Nature of The Beast', it's still better than P4) Win98 SE 850MHz 512Ram 20/60Gig HD (12/34Gig free at present) 32Meg NVIDIA TNT2 M64 I have however only done stills so far (limited time lately) but I do pack my scenes a bit heavy. I close EVERYTHING when working with P4 but P5 seems better, I've even been on-line and ran music...but NOT when I hit Render