I have a problem when editing images in Silver Efex 2 through Lightroom 4.
Once I'm done in Silver Efex 2 and the image opens in Lightroom, Lightroom get incredible unresponsive. If I quit Lightroom and opens it everything is ok again.

I only have this problem on my 6 x 3.33. Mac Pro tower which runs 10.6.8 and have ample RAM.
On my laptop which run 10.8 everything runs smoth..

Maybe it's time to put 10.8 on my Mac Pro as well.... if that's the culprit..