I had this when I first instaled SR 2, poofing during a render or just after it had completed, but haven't had it happen the last two days. (Can't say for sure it's linked to SR2 for me, I found Poser 7 unstable at launch and had gone back to Poser 6 while waiting for SR2).  I'll try deleting lights and applying morphs to see if I can duplicate this.

The things I've changed in the set up, in case they are related to my problem "apparently" going away have been to change the preview display from Scree to OpenGL and I also reduced the number of running threads from 4 to 2. (I have a dual core CPU, try setting it to the number of cores you have). I also found Rendering as a seperate process buggy, so uncheck that if it's checked.

One thing I'll also note is that I was having crashes of Poser or even windows itself (while using Poser) that I was able to trace to the CPU overheating during renders.  The weather was really hot here for a few days and the air conditioner in my room wasn't keeping pace too well, so my ambient temps were higher than normal. My setup uses a pretty aggressive CPU fan (I'm a gamer), so it's possible that some people using stock heatsink/fan and system cooling could be having overheating issues even outside of rendering. Might not explain the other crashes (Unless the CPU is already running borderline temps at idle), but I know it was linked to some (or even all) of my render crashes.

I'd recommend using a CPU temp utility, but unless it's one that came from your motherboard manufacturer I'd be hesitant. When trying to track my heat issues, I tried using a downloaded utility I had seen recommended on a site I visit, because it was less obtrusive than the one that came with my motherboard, but the utility itself caused crashes. :(

On warm days now, I watch the CPU temp during renders and if it reaches 60C I go into the Windows Task Manager, Processes and right click Poser.exe and turn off one of my cores for the process under Set affinity... Poser adjusts fine to the loss of one core and completes the render normally. (This setting doesn't survive the closing of the application). Temp usually drops by about 5C after turning off a core. If it's too hot even on one core, I wait until a cooler part of the day. :)

So, try changing your Preview Render settings from Scree to OpenGL, or even vice versa depending on your settings. Try reducing the number of threads Under Edit/General Preferences/Render (try setting it to the number of cores you have). Also, consider whether overheating may be an issue. (When your cpu overheats, corruption of data will start to occur and some applications will just "poof" under those conditions). See if you have a temp. monitor utility available for your motherboard, or just try to isolate whether the problems are more prevelent on days when your computing environment is warmer.

Hope that helps someone! :)