I too had the same issue, and from this post and others, here is what I did.
I have Admin Tools installed on my site and this problem arises from the
WEP Application Firewall blocking Easy Blog from uploading files.
I consulted the
Admin Tools docs and found an easy fix by creating an exception for com_easyblog.
I wasn't able to get the finer details working for the
view[ and
Query Parameter working so I have just left them blank, which fixes the issue.
Maybe someone else here can provide the parameter setting to fine tune he exception.
Here are the instructions from the Admin Tools docs:
View. Each component has one or several views. When you turn off SEF you see something like index.php?option=com_foobar&view=example&id=1. Note the view=example part in this URL; this tells Joomla! that the view name (i.e. the area of the component we want to use) is example. As you might have guessed, the View option in a WAF Exception allows you to target the exception to exactly one view. If you leave it blank, the exception will match all views.
Query Parameter. Everything after the question mark in a non-SEF URL is called the URL query. You will see a lot of key/value pairs, like id=1, category=1:test and so on. The word at the left hand side of the equals sign is called the Query Parameter. The same-named parameter in WAF Exceptions allows you to target a very specific query parameter. If you leave it blank, all query parameters will be matched.