This is a very common Error if you have a big site in WordPress. Mostly site with huge post count suffers in this error. It could occur while posting new or editing any existing post. I also had this error while creating large sitemap, doing some batch function. You will see any empty screen with the message below –
Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 80 bytes) in /home/*****/public_html/wp-includes/wp-db.php on line 958
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 80 bytes) in /home/*****/public_html/wp-includes/wp-setting.php on line 958
It occurs as WordPress tries to access more memory then its allowed to by “Server PHP configuration” or “WordPress Setting”. Increasing Memory will solve it. Here is solution for all user, who have shared hosting or dedicated or VPS, just FTP access to server will be enough.