I'm on Win98SE and I didn't have any problems of the sort until a couple of months ago. The problem deteriorated during the last month and I had to re-install Poser 4 after I had deleted all the libraries. After I re-installed it, I deleted the default libraries and installed only the stuff that I actually use. Poser 4 seems to work better now but it still hangs more often than 3 months ago. I'm not sure it's an OS problem as it used to work just fine in the past. If anybody knows the answer, please tell us! :-)