Admin Panel error: create/update theme/plugins status not working

Hello,
since the first installation of WordPress into my hosting I’m experiencing a problem related to the ajax progress when I choose to add or update a theme or a plugin (or even update the WordPress version).

After I choose the Update button or the Add button (for example about a plugin), I got the common download page but the page remains stuck like this, w/o noticing anything about the download status (like the loading circle).

https://dl.dropboxusercontent.com/u/5031944/wordpress-admin-panel-ajax-block-2.png

If I wait enough seconds and I go to the Plugin (or Theme) page I can see the the procedure is finished properly, but the installation page remains forevere like the screenshot above.

No errors are shown in the javascript console

I alredy did some test to exclude a bunch of causes, like:
– Using Chrome o Firefox (different browsers)
– Disable all the plugins
– Change the theme (I’m using DIVI) to the default TwentyFifteen
– Reupload the “wp-admin” and “wp-includes” folder
– Dumped the table from a DB to another

But still no solution…

The thing is, I have another site on the same hoster (different domain) and with the same Theme (DIVI) and all this stuffs work fine w/o problems.

And here is the screenshot with the correct log: https://dl.dropboxusercontent.com/u/5031944/wordpress-admin-panel-ajax-block.png

Any ideas?

Thanks
Bye