Had the same problem with Poser 4 on my new system with XP and 1 gig RAM. I was trying to use the 4.18 patch. It was pre-CL I think CL has done two patches, The first one only added the multiple copies check and erased all traces of MC to what 4.18 did. (I think) the last one has fixed things. Until this very latest patch, Poser had a limit on how much memory it would accept on a system. If the system had more, Poser would not load. After you get it up and running, change the attributes for the Poser.rsr to read only. Do the same for the blMilWom.rsr and/or any others you use frequently. (The geometry *.rsr files - the picture *.rsr don't matter. It keeps Poser from corrupting the files if it wants to be naughty.