Can't add media to posts

I have recently downgraded to WordPress 3.4.2. Since then I can’t add media to my posts and pages. I can add media elsewhere, such as Featured Images and Custom Logo,but not directly into a post. When I click on the icon to add media, the pop up window opens and when I am able to select the media I want. If I choose to use it as Featured Media all works as expected, if I choose “Insert Into Post” all I get is a white screen.