This article describes the issue that can occur after upgrading Episerver to use TinyMCE v2. There will be an empty modal when trying to create or edit a hyperlink in the CMS.
It is a symptom of a known change that happened in code.
See "Remove support for legacy dot notation for dojo modules".
If you change in \Business\EditorDescriptors\TripLinkEditorDescriptor.cs to
ClientLayoutClass = "epi.shell.layout.LayoutContainer",
then recompile the site, reset the application and reload and tested the modal will work again.