I have a similar problem, in my P6 if I click the inventory listings in the menu a little bit to quick/often it tends to freeze the menus up, I have no way to recover that then to restart, most of the times I can save the peice since the drop downs still work, so it's just the right hand menu that craps up on me.

My own theory on all this and the above is due to poor memory management inside Poser
6 has turned a bit better then 5 , in 5 I had the above problems all the time, what I did notice
is that even though you have 4Gb RAM avoid running other programs in the background and also check your anti virus programs , I turned min off at times and that seems to release some files that I think are locked up by it.