[tex-live] Debugging TeXdoc on Windows (TeX Live 2013)

[Philip Taylor]

My TeXdoc has stopped working; trying (for example)

	TeXdoc Makeindex

from the TeX Live 2013 command prompt results in nothing.
Inserting the "-l" qualifier yields :

 1 D:\TeX\Live\2013\texmf-dist\doc\support\makeindex\makeindex.pdf
 2 D:\TeX\Live\2013\texmf-dist\doc\support\makeindex\ind.pdf
 3 D:\TeX\Live\2013\texmf-dist\doc\man\man1\makeindex.man1.pdf
Please enter the number of the file to view, anything else to skip:

and entering

	1

just takes me back to the command prompt.  Adobe Acrobat remains
resolutely unlaunched.  File type associations appear to be normal, and
double-clicking on a .PDF file in an Explorer window will launch
Adobe Acrobat in the normal way, as will (for example) entering the name
of a PDF file in the current directory from the CMD prompt.
How might I best go about tracking down what has gone wrong ?

Philip Taylor