Well I see two issues here, one is the open_basedir restriction. This is something that you (if you have Apache knowledge) can change in your vhosts.conf file, or you can ask your hosting provider to do it for you. Chances are they'll have no problem doing it.

The other issue is file permissions, or the file location itself. If you're sure you've setup the File Downloads folder correctly, /admin/store/settings/products/edit/features (File Downloads config), then it's a permissions error.

I would setup your Downloads folder to look for an absolute path, in other words:
/home/upstre5/public_html/folksongsingalong.com/files

(make sure there is a directory here and that you have given it global read/write permissions - you can do this easily in FTP software, such as FileZilla, by creating the directory, right-clicking it and choosing Permissions)

open_basedir restriction basically means that, "PHP is only allowed to access files from within this directory and its subdirectories" and if you try to grab a file from outside that protected directory, you get that restriction error. This is mainly helpful if you are storing your files outside the public_html folder, or "webroot".

I hope this makes sense, feel free to ask more questions if you still need help. You might try searching the forum as well, since your problem is not an uncommon one Good luck!