If I remember correctly, the OE uses Javascript to pop up various dialog boxes (insert link, object, etc). Please check that you haven't disabled Javascript support in your browser (or that the browser you're using actually supports Javascript). Just a question: did it work all well until now and suddenly stopped working (on the same computer)?
Make sure that the user has permissions for the ezdhtml module, you are allowing .js & .jar files to be retrieved from the file system in the apache rewrite rules (As per installation.txt) , also the permissions of the files under extension/ezdhtml should be readable by the web server user.