Hi,
I am having this same problem.
Intel Core i7 2600 with 8 gig ram, nVidia GTX560Ti with latest drivers.
Just reinstalled it and it didn't change anything. Read elsewhere that reducing number of fences helps, but made no difference to me.
I noticed that when I drag a fence, the explorer.exe process uses an entire core at 100% for the period, and has about 5 seconds of delay between my dragging and it following, like the fence is being dragged through molasses by a rubber band.
Anywho I think you guys know exactly what the problem is and I dare say you've fixed it, but I don't think the free version (which is what I have) has been updated since you fixed it. The free version is at 1.01 and the Pro version at 1.10.
Do you think you could push the updates to the free version so we can all have molasses free fences?