After it’s absolutely clear that there is a problem with the new version of wp especially with the save option. For me the only solution is to use the old wp-db.php but this is something like a temporary solution. I’ve deactivated all the plugins I use, I’m not using a cache plugin and I’ve cleared the browser cache. So it’s not a plugin problem. So I need some suggestions about the required mysql version so I want to be sure that it’s not a hosting issue.
Thank you all for the possible solutions but even the manual reinstall of the wp version didn’t resolve the problem.
Also what is an error 1484 in formatting.php and what can cause such problem when I want to edit a page.
