Since it seems that Paul has been busy this weekend and unable to check this for you, I went ahead and checked it myself.
I can confirm that it is still too quiet, still in mono, and (less importantly, but still important) the file name has one or two errors.
In order to keep this project moving and allow you to move on to other things, I'm willing to fix these things and reupload it myself. I just need Paul to confirm that it was in fact PL ok other than these tech issues. It looks that way, but I want to be sure.
I wish I could give you some suggestions as to what is causing the trouble with this one file. I see that you have had some similar issues in other projects, although your one-minute test went off without a hitch. Have you changing anything in your recording setup since making that test? Either hardware or software, or maybe in your process? If so, it would be worthwhile to do a new test with your current setup. If not, all I can say is that you are not the first volunteer to have trouble with GarageBand not wanting to create files in the format we need.
I wish I could be more helpful.