This has been bugging me, but I can't reproduce it on the demo site (which I've found is key to actually getting an answer!) I just realized, however, that it's totally reproducible here on Unity!
The image upload popup boxes and the hyperlink boxes are the incorrect sizes. In order to hit "insert" I have to resize the boxes every time. How can I resize these boxes?
The image upload popup box looks like this:
(notice the missing "insert" and "cancel" buttons!)
And the hyperlink popup box looks like this:
(again... missing insert and cancel buttons)
(I've attached the images below also and the resized boxes in screencaps as well so that you can see the missing buttons once I've resized each popup window.)