P5 needs a lot more memory. I have both PP and P5 on my computer, for precisely this reason. For scenes with a lot of characters, or very large textures, PP will handle scenes that P5 chokes on. But all in all, I prefer working in P5. I like the interface better. I like multiple runtimes. I love the power of the cloth room and the material room. And atmospheric effects! But when I want to do a render of the entire Dallas Cowboys football team, I don't do it in P5. There are ways to tweak your settings to maximize memory and speed things up. Make sure you have the latest service release installed. (And hopefully, SR4 - due at the end of this month, hopefully! - will fix even more problems.) Make sure your swap file is the right size for your system. Keep your main runtime lean and mean; install stuff into other runtimes instead. (Since you can, with P5.) Remove Content Paradise. As for the lights - it may be a memory issue. I've noticed Poser does weird things to the default settings file when it's having memory problems. I can switch between P5 and PP with no problem. (Though I've noticed that they open with different default cameras as the default.) I've never used P4, so I don't know how well it plays with P5. Why don't you post your system specs? People might have suggestions for you. CPU, hard drive space, RAM, OS, etc.?