postscript output with psbook and psnup

[Frédéric Bron]

Do you know why the postscript files produced by lilypond (2.10.33, 
cygwin) are not compatible with psbook and psnup?

To prepare the printing on A3 paper, I used to do the following with 
lilypond 2.6.0:

psbook score.ps | psnup -2 > score.2.ps

With the output of 2.10.33, the output of psbook cannot be viewed with 
gv: the file has a size comparable to the original but gv shows a blank 
page only.

F. Bron