silverstripe/sapphire — pull request #954 by dospuntocero (2012-11-15 20:59:58+00:00)
Title: FIX - http://open.silverstripe.org/ticket/7646

please update this file ASAP, this bug is a real blocker.
http://www.silverstripe.org/data-model-questions/show/20146

If I come in on new session, login, go to the model admin and then choose to add a link, seems to work just fine.

This is because you're working with the cached version of the HTMLEditorField from Pages in this moment. If you ?flush the ModelAdmin, a new cached version for ModelAdmin will be created and the link to MediaForm and LinkForm in ModelAdmin will fail.