Major Lagging with Waves plugins and Open Video Window

[dreamuse]

Well, this is an interesting situation:

I'm running DP 9.51, and am using waveshell 9.91. I'm finding that when I'm using a Waves plugin and don't have a video window open, all virtual knobs, sliders, and other items work snappily. However, once I have a window open, all knob moves become quite slow and stepped...I'm seeing an update only every half second or so. If I kill the video window, the problem goes away. If I take the waves plug out, the problem goes away.

Anyone else seen this, and/or have any thoughts?

Much thanks,

Len