Hi Adam,
This is interesting - I see this in Internet Explorer but not in Firefox or Chrome.
I'll have our web team take a look - I'm guessing either the server or the browser isn't properly handling the MIME type for VSS files.
In the meantime, you should be able to download them by right-clicking links and using the "save target as" feature. Just be sure to manually set the file type to *.vss.
-Drew