Cannot manipulate UVs in the UV editor viewport I am unable to select or move UVs through the UV editor. Pressing any of the selection tools (B for box C for Circle and Ctrl-RMB for Lasso Select) does nothing and does not appear in the viewport.  I can manipulate the UVs outside of the UV editor and by using the circle selection option, under the Select tab but I am unable to do anything further. This issue occurred after I was UV editing my object and happened for seemingly no reason. I have tried to undo the affair by unselecting the options on the toolbar to no avail. 
I am using Blender v2.79.
You have UV Sculpt enabled (hotkey is Q, maybe it's not terribly hard to hit it by accident)in the UV Editor's &quot;t&quot; panel. Hit t to show the panel, navigate to options tab and disable it or just hit Q while in UV Editor to get out of UV Sculpt mode: