I have just upgraded Magento 1.6 to 1.9 and everything went as smooth as baby’s bum (or silk).
But there is one issue. I am not able to insert images using WYSIWYG editor. The “Media Storage” dialog box is showing up wired. Look at the screenshot below:
Solution:
There is a CSS file called magento.css inside the directory skin/adminhtml/default/default/lib/prototype/windows/themes that is missing on the upgraded version. Move in the file to the new version same location, problem solved!