zip file corrupted

Hi, this error is probably not due to the archive class, but hitscounter (from phpclasses.org) which I use to download zipfiles from the server. Archive.php creates zipfiles which self-unzip using windows explorer on my own PC, but when I download them from my site using the hitscounter class, explorer tells me they are corrupted and won't open them. Hitscounter works fine for other files. Is there something specific that needs to be done to zip files in order for them to download properly, and be self openable, using a php script such as hitscounter?

There is no forum for hitscounter.

Hope you can help. Downloadable zip files on my site can be found at http://www.passingphase.co.nz/eparty/page2-Education.htm, go to 'options' on menu bar, click on 'save as html file' and then click on the file eparty_policies, which is the zip file created using archive.php.

Kent

Oh, and I have made sure that the following header applies during the download:

header("Content-Type: application/zip");