User Evad37 on the English Wikipedia reports:
"Images which are not thumbnails can't be edited properly using VE. If there is a single image, it can be selected, but the resize handles don't appear and the media icon doesn't appear. Moving the image around works and deleting the image works. When there are two images like this, the mouse pointer turns into a "forbidden" symbol (the mirror image of ∅), with the tooltip "Sorry, this element can only be edited in source mode for now.", and semi-tansparent shading covers both images. The images can't be moved, and can only be deleted as pair - you can't delete only one image. I am using Chrome (v. 28) on Windows 7, and was playing around with VE on List of freeways in Victoria, Australia."
I was able to reproduce this using Firefox 22 on Xubuntu Linux, so seems browser and OS independent.
I presume that the issue they note with regards multiple images is that VE is treating them as a gallery, which it doesn't yet support. This might therefore depend on Bug 43037