For me also installing the older cups-pdf version from the Hardy repositories did the trick. And a new feature: The PDFs thrown into the ~/PDF directory now finally have useful names, apparently taken from the printing application's window title. In Intrepid all PDFs hat the name and window title "_stdin_", which was sort of ugly, but well, better than no PDFs.

One thing I noticed, though, when installing the Hardy version of cups-pdf through Synaptic: as a dependency the package named "cupsys" had to be installed with it, though it was taken from the jaunty repos. Jaunty's version of cups-pdf seems not to depend on this package. As a test I removed all cups-pdf and cupsys again and re-installed cupsys additionally to Jaunty's version of cups-pdf, but that didn't change a thing. No PDF would be created, no matter if ~/PDF existed or not. So, now I'm back to Hardy's cups-pdf, which works just fine.

I guess, for some machines they simply broke cups-pdf in Jaunty...