Hmm, that's really a strange one..
I have another server to upgrade, let's see how that one goes for me =)
// Update: I just upgraded an installation from version 0.5.1. The script recognized the correct version and the upgrade ran through perfectly.
Maybe you should do the manual upgrade and hope that with the next upgrade you can use the script. Or, but I really don't think this could work, but try to download a fresh iniset.php file from the 0.7.2 package and replace it with the one in your install. Maybe there are some kind of encoding or formatting errors in the file. But i think the script wouldn't even care about that. That's what I would try now, even though the chance of success is pretty small =)