I've been using this technique for weeks - attaching SW drawings to the ECO (.xlsx) file that is being used to release them.  It has never given me any trouble, but somehow today the feature has taken a hike.

I select and copy the drawing file, check out the ECO (xlsx) file and RC/Paste as reference - except that for some strange reason 'Paste as Reference' is greyed out.  Simply not available.

None of the files are checked out by any other users nor are they open in any other applications.  I've tried it using my usual account and with the all-powerful Admin account.  EPDM just says no way.

I'm sure I'm just missing something obvious, but I'm too tired to find any problem right now.  When NOTHING HAS CHANGED, what could cause Paste as Reference to suddenly become impossible?