File downloads

I've got membership setup perfectly. Except file downloads. I thought it was working great until final testing just before tomorrow's launch!!!

Here's my problem:
I've added a couple of protected file groups.
I changed the url in Membership's settings to /member-downloads/

I inserted links to the files in the content. When I insert using WordPress' default, /wp-content/uploads/2012/5/filename.zip, anyone can download the content. The url is not masked to /member-downloads/

When I insert change the file link from /wp-content/uploads/2012/5/filename.zip to /member-downloads/filename.zip, users without the appropriate access get a no access graphic. Users with access however get a 404 error.

I've tried resaving the permalinks, which are set to postname, but it didn't make any difference.

I'm ready to launch a new site selling a theme for churches tomorrow morning! Please help!