My LR was automatically updated to version 6.6 last week. Since the udpdate, the Develop/Sync function does not work. When I select images and I click on Sync or Sync Settings button, the LR freezes immediately. I can restart the application just after killing it from Windows task manager. It is very annoying, I need to develop sever hundreds of images and without syncing common settings, it is very-very slow and not as accurate.
I have already tried to switch of GPU acceleration, as it was suggested in forum for former similar issues, but unfortunately it was not cure for my problem.
I use LR on a Windows 7 x64, i7 CPU + 64GB RAM, with GTX680 GPU