I fanally got this resolved over the weekend - or at least I figured out a work around for it. It turned out to be the way I was constructing my install file. I use Inno Setup to build my install package. I had the following set in my [Setup] section:
I was able to get it to finally work by changing my Inno script to use:
I am assuming there’s something about the lzma compression and/or the SolidCompression setting in Inno that goofed up Magento. Everything else I have that downloads files worked okay with it, but Magento didn’t like it. I wish this could be fixed in Magento because now my install files for download are a good 50% larger. I guess I’ll have to live with that unless the Magento guys can fix it at a later date.
I hope that helps someone else.