Cannot upload/insert image into post/page

Hi,

I’m currently making a website for a client, using WordPress version 3.1.4 (the client’s server doesn’t run MySQL 5.0, so I can’t use version 3.2), and I’ve encountered a problem I hadn’t seen before.

When editing a post or page, clicking the “Add an image” icon above the text field doesn’t do anything. The desired pop-up doesn’t show. The same goes for add video/audio/media. I can however open the link in a new tab. But then, when I click “insert into post”, the screen goes blank and the images doesn’t get inserted into the post.

I’ve made a backup of my files and ran a clear WordPress install (twice), using a new database, but the problem stays.

Another problem I’m having is I can’t enable any fields under “Screen options”. When enabling them, nothing happens. I’ve found out how to manually enable them using functions.php, but I thought this might something in common with the above problem. Also drag and drop in the widget and menu area doesn’t work.

My guess for now is there’s something wrong with the server, since I’ve never had this problem before on other servers, but I’m not sure. Does anyone have any suggestions?

Thanks in advance!

– Leon