Hi,
I had the exact same problem as described.
It might help reading this
forum entry
from Joomla to understand why it is throwing this particular error.
I was able to solve my issue by editing the file:
administrator\components\com_jedchecker\controllers
Find the line:
if (!JFile::upload($file['tmp_name'], $file['filepath'])) {
and replace with
if (!JFile::upload($file['tmp_name'], $file['filepath'],false,true)) {
This will let Joomal know to upload unsafe files as well.
(I also added .zip and .ZIP to the Media Manager Settings, but I am not sure if this is important)
Hope that this helps
Kind regards
Yosh