Recently I tried to upgrade from 1.5.0 to 1.5.1, but I had to downgrade at last, because PDFCreator.exe seems not to be registered correctly as "PDFCreator 1.0" COM object (Windows XP SP3 / MS Office 2003 Professional).
After reinstalling 1.5.1 twice with no effect I decided to downgrade to 1.5.0 again. Referencing the COM object works well with 1.5.0.