PDFlib output

I am having difficulties moving a block of code from one machine setup to another. The code uses the PHP PDFlib functions to generate a PDF file online. It runs flawlessly on a machine running Windows 2000, Apache internet server, and PHP 4.2.1. When I try to run the same code on a machine running Win NT 4.0, IIS, and PHP 4.2.3, the code runs very slowly, only sporadically, or more commonly, not at all. The program also uses the ODBC connector to return records from a database. This process works well using only PHP and ODBC. However, when the PDF functionality is added in, it seems NOT TO RUN ON THIS PARTICULAR MACHINE SETUP (whereas, again, it runs well on Apache). Any solutions or ideas would be greatly appreciated. Bill