[NTG-context] inclusion from image database broken (mkii+mkiv)

hi, when i try to include an image from one of my databases i get the following error messages: mkii: !pdfTeX error: pdftex.exe (file ./lib/test-db.pdf): xpdf: reading PDF image failed (0) ==> Fatal error occurred, no output PDF file produced! mkiv: !luaTeX error: xpdf: reading PDF image failed ==> Fatal error occurred, no output PDF file produced! i looked into the mkiv sources, but didn't succeed. the lua part (db only) is clear to me, but i couldn't find the point in tex, where \externalfigure is mapped to this somehow. either i have missed something or there is some code missing. mh, probably the first one :) regards, peter ps: any news about the \string{\{} problem in mkiv?