After reinstalling everything again I discovered something. When I deactivate another plugin (WordPress Firewall 2) the media library works perfect again.
I apologize in advance if the issue is coming from this other plugin. I’m sure I deactivated before (on previous re-installs) and it didn’t solved the problem. Also as I mentioned before, on previous reinstalls it worked OK until this error seems to come from nowhere, so I’ll let this plugin down for a while and cross fingers that the error is gone for good.
I’m sorry I can’t be more specific right now.
