I am having similar issues.
I have been working on a site for the last few weeks. Everything was fine. But today Muse CC 2014 started to freeze every minute. Whenever I tabbed out of it or wanted to bring in new elements it freezes for about half a minute.
It really is a pain trying to work like this.
I have already re-installed Muse and re-named the project without any effect on the performance.
Help please