Same slowdown here. And I have a modern nVidia card (6600 GPU with 256 MB) and using the very last drivers from nVidia.
6 WinterQeens (Jessica) are consuming my 1GB memory.
Any action I execute (anywhere) is also consuming 100% of my AMD64 3200.
In the Keyframe Editor, I see a similar slowdown as yours.

I use CATIA (a heavy CAD to make airplanes and I don't see CATIA puting this system on the knees like Poser6 is doing).