add media – not able to upload anything

All of a sudden I cannot upload any media to my blog.
I write the post then when I click add media the box pops up, but if I click “select files” nothing happen, I can click on the tabs above like gallery and see images, but when I click “show” again nothing happens.

I don’t know how to resolve it. It has appeared overnight, no new plugins have been added or upgraded. I have tried on Chrome, Internet Explorer and firefox. all have the same issue.

Cleared cache and cookies – still the same issue

Checked with my host

accessed from my wordpress.com account – This issue is still not resolved.

Any help would be gratefully received.