https://groups.yahoo.com/neo/groups/QuadtoneRIP/conversations/messages/13210
the whole point of the virtualstore is that you don't need admin permissions to save files in it, whereas you do if you save qidf and quad files in the 'Program Files' hierarchy alongside the files that ship with QTR.
So the spinning wheel in W10 is a bug rather than a permissions problem. One that can't be fixed without the original author, who was not Roy.
There are two workarounds - restart as John discovered, and 'save as' the file elsewhere and then move it into one of the locations described in the link above.