Docbook 5 bibliography errors

I have recently encountered 

[Nix09] Error: no bibliography entry: Nix09 found in http://foo:8080/bibliografi/data/biblio.xml

whenever I generated with xsltproc on a Linux (Sheets 1.75.2)

then I changed to saxon and it went smooth for a while.

Now I am breaking in old macbook Pro, and the problem came back. This time not only with xsltproc, but also with saxon transformations.

Anyone?

I have been googling like a mad, but the only thing I found was similar errors on several OASIS pages, shame ;-)

/Niels Muller Larsen