One day discovered that WP-Super Cache was not working correctly. The plugin didn't create any cache files nor giving me any errors back.
I went through a list of 20 plugins, one-by-one, and I discovered that plugin WP-ContactForm version 1.5.1 doesn't work correctly with WP-SuperCache. Only inactive WP-ContactForm plugin let WP-SuperCache to produce cache files.
So if you have both and WP-SuperCache is not working for you I hope I saved you some troubleshooting.