Thanks fo rthe help. It looks like I was trying to upload a file with a formidden suffix, an executable. I was trying to make a zipped, self extracting, file available to users of a site I'm building. I found a solution, a joomla extension called nicepaypaldownloads. I'd actually bought it for a different site I'd built earlier this year and the terms of the vendor allowed use on multiple sites and the abililty to download a current version,
Again, thanks!