I am getting this now when I try to make changes. Was working fine all of a sudden stopped.
The preview could not load. This is most often related to a plugin conflict or aggressive page caching. Checking the developer console for errors could indicate what went wrong.
It seems to be something wrong with the theme, as i have been making changes over the past 4 hours then it crashed?
Its ok I found the cause of the problem, was a security software