With OS X, one other possibility is excessive use of VM. The problem is that, in trying to run top or VM_stat in terminal (or watch processes with whatever process-viewing GUI you have), Poser 5 is so poorly written that it may be difficult or impossible to get a valid reading on virtual memory usage before Poser crashes. The current VM setup is such that if slowdowns occur, it's usually necessary to restart, because there's currently no safe way to "reset" the VM process on the fly. I agree - go into System Prefs and do what Marianne said. But I believe Poser 5 is beyond salvation, and that we have to wait for a complete rewrite to bring it up to speed with other OS X apps.