Images disappeared from the site

First I want to say hello to everyone cause I’m posting for the first time here. Never had such a urgent need like this one here so…

Back to the topic. Recently I updated one of my WordPress sites to 3.8 version. From that moment I had problems 1) first with uploading media (known issue – error – “Try again later.”) and 2) now even the existing images disappeard from the site. I’ve been reading since yesterday what could be the case. I tried plugins deactivation, changing permalinks, changing permissions and eventually downgraded to WP 3.7.1. But guess what? Nothing helps.

I can still see the thumbnails of images at the media library but when I click on them I can only see a blank page. Direct links to images show 404. But media files are still there at:

/public_html/wp-content/uploads/2014/01

I’m not a WP nerd but I guess that there’s just some kind of small interference on the line between media files and some WP settings.

Please help or I’ll shortly become bald because of it.

Thank you in advance.