When I updated to 3.9 I could no longer use the media, text, or visual tabs in my posts. I followed the suggestions of deactivating all of my plugins and then one by one add them back in and check the functionality of the tabs listed. I discovered the plugin that was causing the problem was Inbound Writer.
I appreciate all of the suggestions to solve this problem. I am going to the author of this plugin and find out why I am having the issue.
I also cleared out all of my cookies before I deactivated the plugins