Yep, I have all Friend Areas, my leader is level 100, and I hold a Friend Bow when I beat them. According to an FAQ on Gamespot, that means I have a 34.1% chance of recruiting them each time.
What I mean is since they're instrumental (no pun intended) in putting together the Music Box, that maybe you need to do something extra like bring the Rock/Ice/Steel parts with you, or a pre-made Music Box or something.
EDIT: I've just recruited Regice, so I'm obviously doing something right. =)
EDIT AGAIN: He just fell down a Pitfall Trap, now I have to go get him again! Damn it!
YET ANOTHER EDIT: Well now I have Regirock permanently.
Anyway, new question. Anyone know if it's possible to get more than one Mew? Since you just need to walk around Buried Relic with a Music Box it seems plausible that you could get a couple.
23/04/2007
Pokemon Diamond
Sydney, NSW