I have logged in and disable BWP Minify plugin. I was successfully able to edit a page when the plugin is deactivated.
Please keep in mind that we already have minified the JS and CSS files in the theme. Having to minify those files again could possible create an issue which would prevent the Cornerstone to load. I would recommend that when you edit a page or still just developing the site, please disable any caching and minify plugin. There are best turned ON when you are finished building the pages and ready to make the site live.
Hope this helps.