Just spent my entire day w/ the same problem, but I have it fixed now. I just want to "Pay it Forward". Finding a fix for this is like a needle in a haystack,, but through my 7 hrs of research,, only ONE thread out of Very Many gave me an idea of what to check.
-Turns out, there was an application in the background that kept Crashing every 10-15 sec. Every time it either crashed or tried to start again, it took the computers attention away from my current window and on to IT. The Post I read said that in their case, it was an Auto Backup program of some type.
In my case, it turned out to be the same thing. An Auto Backup program from Cox communications. To find what's troubling your computer,
1. close all your Apps
2. Open Activity Monitor
3. Sort columns by CPU
4.Keep a watchful eye for what keeps starting & Crashing
5. Double click on it or try to open it any way you can (Immediately while it is trying to open) and work on getting it DELETED or Uninstalled
a. Before you delete it, you can also try "ForceQuit" first to see if that helps. In my case, It kept re-opening even after Force Quit, but Uninstall worked
perfect. With this info, you can at least walk in to any Genius Bar @ Apple store and give them a huge head start on the problem, IF you are unable to complete the task.
I hope this helps! There's hardly any information to find on this problem, so SHARING this info in another thread or elsewhere would be a thoughtful thing to do. ..
Safari was my culprit !!