501 error when Add media to post

I am using WP 4.0, I cannot add media to my post in both visual or html mode.
When I use html mode, it feedback with this screen:

https://www.oneandonebd.com/wp-content/uploads/2014/10/Screen%20Shot%202014-10-13%20at%202.36.45%20pm.png

When I use visual mode, click on the Add Media button, no response at all, the developer tool state that is a 400 Bad request:

“https://www.oneandonebd.com/wp-content/uploads/2014/10/Screen%20Shot%202014-10-13%20at%202.50.07%20pm.png

This ia a brand new website, without any plugin activated.
Using theme: Twenty Twelve

I ve tried reinstall WP, cannot solve this problem.

Please Help!! Thank you!