Lightroom :: Convert Nikon D90 Raw Files To DNG

I did a search and couldn't find this issue listed. I convert my Nikon D90 raw files to DNG. Never seem to have a problem with that except that the display(s) seldom shows the results of applying Noise Reduction (Color or Luminance). If my display is at Fit or Fill I don't see the results of what I am doing. If I zoom in to 1:1 or more, then I can see the results. All works fine if I am using a jpg file, it is just the DNG files that do this.

If I want to see the entire picture with Noise Reduction applied I have to switch to the Library Module. Then when I go back to the Develop module the main display goes back to not showing the Noise Reduction, but the secondary display is ok until I apply another effect then boom, back to Noise Reduction not displaying. All of the other changes I make work just fine. It is just the Noise Reduction that causes the problem. This is really a killer when I am working on photos. This problem existsed before 3.6. When I switch to the Library Module it takes a few seconds before the secondary display shows the photo with the Noise Reduction applied.
 
I have a quad core 2.4ghz with 8gig of ram and Windows 7 Pro 64bit OS. Plenty of CPU and memory available.