In 8.0, with no plugins and 2014 theme - I have a page with an image already embedded in it. I also experienced this issue in 7.1 with the 2013 theme (which prompted the upgrade).
I click the image icon in the image and through the menu I can change the alignment, and update it.
But as soon as I insert anything into the caption, the alignment gets removed from the image, and the caption entered is never shown.
Here's a short video demo:
http://screencast.com/t/WryWFiq3l
