[Zope] problems with Zope rendering PDF Files

Hi, Has anyone had problems with Zope not rendering PDF files properly? The pdf files are in a localFS object in Zope and are opened within the browers. Most files are ok but I am recently having problems with a couple of files. I get a "File is damaged and could not be repaired" message when I try to open it within Internet Explorer or Opera. The file is fine when I open it via the acrobat reader. The file is from an external provider so I cannot make changes or try to regenerate the file. Any assistance would be greatly appreciated. Regards, Rhian