That sounds like something is corrupting either the .dyn file or the temp file generated during the simulation. Is there anything running in the background that 'protects' you from file changes? That temp file can retain old data, and conflict with what the PZ3 is telling Poser to do. On the first issue, have you deleted first the temp file, and if that fails, the dyn file? I've noticed that once something in them is changed or altered, its impossible to fix them, and rewriting over a damaged one just makes it worse.