I'm assuming that you're referring to Maintenance Release 7 (MR7). I've run into this in the past and the way I got around it was to reboot the server and reinstall. Don't know why it fails the first time around, but the second install has always worked. As a side note, I'm not certain that you need MR7 installed to move to BES 5; I'm sure someone here will chime in with information. Good luck either way you go.