Cannot create links in new posts

Hey hdgross,
If the visual editor is not working, it is probably because of the Javascript error caused by one of your plugins. Turn off your plugins and see if the visual editor is working ok.

Also the suggestions made by esmi here will help you resolve your issue.
http://wordpress.org/support/topic/wysiwyg-not-working-in-visual-mode-for-posts-pages?replies=2

Please let me know if you still have the issue.