Bit of a fishing trip, have you..

Checked the event logs to see what (if any) error messages are displayed

Run dxdiag and clicked on each to screen (No problem found should be displayed in Notes)

Configured Poser to use only one thread for Rendering (incase this is a problem with your CPU)

If your PC comes with any stress software have you ran this since the problem started. This should go through all your components and memory.

Revert you video driver to the version running before the problem started.

One thought is trying to reproduce the problem in safe mode but I don't know if there are any risks in doing so. The reason to do this is it removes all third party drivers from your OS in one easy step - done at your own risk, I not saying you can/should do this but its an idea to consider.