I can not send images from LR4 to any external editor via Photo>Edit In. My system is Mac OS 10.7.3. Using the Edit In command fails to open the external editor and no error message results. This occurs whether the images have the 2012 Process Version applied or not. My external editors are primarily PSE10 and Nik Silver Efex Pro 2.0. This is an important part of my workflow.
I have reinstalled PSE10 and updated to the newest version of Silver Efex Pro.