I have Photoshop CC 15.1.2 installed (Windows 10 x64) and I have a problem editing smart objects, actually a specific one. It's is a smart object created in Photoshop containing like 2 groups of ~10 vector layers. When I double click the smart object (or right click --> Edit contents) it opens the "New document" dialog. When I click Esc it closes and opens the "Recent Files" dialog. It works fine in CC 14.1. I have no idea why this specific one isn't editable, but I'm pretty sure it worked before last update.