I don't think it's your memory sticks. I've been running into the exact same problem you described. I recently got a 2.6 GHz computer (Pentium 4) with 1GB memory and everything was running fine until I started working with large files in Poser 4 (80 to 100 MB in size) and 3-5 characters in one scene. Poser would keep popping up with error messages that I've never seen before even in my older slower machine. Then the textures for characters and props would disappear leave only the models. The windows boxes would appear one after the other and I would have to shut the system down completely and reboot. I also tried the Poser 4 memory update and this is when I first noticed the problem after installing this update. At that time, I uninstalled and reinstalled Poser 4 and the problem seemed to get worse. I formatted the hard drive and reinstalled everything and just recently I noticed that the problem has crept back up. I don't have the memory update installed this time. I wonder if it is file related, even though this happens with newly created files.

Poser 2, 3, 4, 5, 6, 7, 8, 9, 10, Pro 2014, 11, 11 Pro