[NTG-pdftex] PDF images : any limit to their number in PdfTeX (Win-32, TeX Live 2007)

I am endeavouring to typeset a book which will include between four and five thousand PDF images (included using \includeimage from package "Graphicx"); PdfTeX (Win-32, TeX Live 2007) is bombing out with no error message, and I am concerned it may be hitting some limit. Is there any known limit, and if not, does four to five thousand seem reasonable ? I should add that each of these images forms a part of one row of an \halign ... Philip TAYLOR