WP-Cache and 0 cached pages
As I wrote in Make WordPress fly article, WP-Cache can make WordPress very fast. I have been monitoring my www.redips.net and discovered that WP-Cache doesn't work. Directory wp-content/cache was empty (only wp_cache_mutex.lock file was inside). In WP-Cache control panel was written 0 cached pages and 0 expired pages (WP-Cache was enabled). File permissions and WP-Cache configuration were intact. No one was touched anything, but WP-Cache didn't work any more.
After checking files, I found that symbolic link advanced-cache.php in wp-content directory was pointing to non existing location instead to wp-content/plugins/wp-cache/wp-cache-phase1.php file. I corrected symbolic link and WP-Cache started to work.
How to restore advanced-cache.php symbolic link?
My first fix attempt was to replace symbolic link with pointed file, so I deleted wrong advanced-cache.php symbolic link and copied wp-cache-phase1.php file and renamed it to the advanced-cache.php. After that, WP-Cache started to work! Oh happy me! 
But after listing files in wp-content directory, I saw that advanced-cache.php file was rewritten with correct symbolic link. Hmm, that was even better, but who did this?! Then I deleted advanced-cache.php symbolic link and went to the www.redips.net home page but WP-Cache wasn't work. After accessing WP-Cache control panel, link was recreated and WP-Cache was working. He he, I deleted symbolic link again and I listed wp-content directory. After accessing WP-Cache control panel, symbolic link was restored. So, to restore advanced-cache.php symbolic link please follow this steps:
# How to restore advanced-cache.php symbolic link in wp-content directory? 1) delete advanced-cache.php symbolic link 2) access WP-Cache control panel
Why was advanced-cache.php symbolic link changed?
Hmm, changed advanced-cache.php was pointing to some non existing backup location. The reason can be because of restored backup. My hosting company didn't send any warnings, so I am not sure if they did backup and why - it's my guess. Anyway, advanced-cache.php was changed and I will pay attention to it. If you have similar issues with WP-Cache, please share your experience. Thank you!