[NTG-context] 2DOWN imposition gives blank pages

I'm learning page rearrangements and cannot figure out why the following small example doesn't work (it's similar to those in the cont-eni.pdf manual, fig 3.22). Here it produces a two-page, blank PDF file when I run 'texexec --arrange p2' [ConTeXt ver: 2006.08.08 21:51 fmt: 2006.8.8 int: english mes: english] \setuppapersize[A5][A4] \setuparranging[2DOWN,rotated] \setuplayout[width=fit,margin=0pt] \starttext \input tufte \input tufte \stoptext