This error usually results into a plain white screen with no error message. This makes it the most puzzling because you have no clue where to look and what to fix.
Most of the time it is caused when a script exhausts PHP memory limit. It can also happen due to a configuration on the server.
Solutions: a) Increasing the Memory Limit
b) Disabling All Plugins
c) Replace Theme with a Default Theme
d) Or in some servers you will be required to modify your PHP.INI file.
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