Insert into Post button disappears when trying to upload images already used

I’m trying to insert images into pages. I click on the “Add an image” icon. I click on “Media Library”. I find the image I want and click on Show, then click on “Insert into Post”. If I want to use that same image on a different page, I go through the same steps as above, but the “Insert into Post” button is not there. Just “Delete”.

Is this a bug in WordPress 3? Why is this not possible? I have other sites using version 2.x and I’m able to insert the same images in multiple places.

Yes, I have disabled all plugins, cleared cache, tried the default theme and I still have the problem.

Is there a fix?

Thanks