This is a strange one, but I thought I'd report it anyway. Feel free to close as I imagine it's impossible to repro.
Running r114 and my graphics driver crashed (GeForce GTX 550 Ti). After restarting my 'back', 'done' and 'cancel' buttons had disappeared. Reinstalling didn't fix the issue either.
<img src="http://i.imgur.com/7pK9G.png" border="0" />
I fixed it in the end by deleting registry entries.