"Insert/Edit Link" button not working

I used to be able to highlight text and click the “Insert/edit Link” button to create a hyperlink in my site. I disabled all plugins, and it still didn’t work. There are other features that have stopped working as well, including: Slide Set Manager (it doesn’t have the same old format where I can select images), and Product Tags (I cannot add product tags while in the “Edit Product” page.