In the next days I upgraded to R6 (from R3) a Nortel/Avaya BCM 450.
After this upgrade we have verified that is not possible to add wav file for MOH: we got the following error.
"Playlist ADD failure: list output error"
To resolve the issue the following steps below.
1) Reboot the system
2) Re-enter with Avaya Business Element Manager in the pbx
3) Take a screen shot of Configuration->Applications->Music
4) Administration->Backup and Restore->Restore from: Factory Default & select Restore button.
5) Select OK.
6) Take care to restore only ‘IP Music.’ Verify that only IP Music has been selected, then respond Yes to proceed with restore.
7) Restore complete – Select OK
8) Select Configuration->Applications->Music and submit the value like 3)
Now you should be able to add wav file to play list !
Att.: I think that you can follow the same steps for Nortel/Avaya BCM 50 too, but I have not tried.