mpd5/Netgraph issues after upgrading to 7.4

[Przemyslaw Frasunek]

[...]
> Mar 31 13:48:06 lsm-gw mpd: [B-150] Bundle: Interface ng149 created
> Mar 31 13:48:06 lsm-gw mpd: [B-150] can't create ppp node at ".:"->"b150":
> Operation not permitted
[...]

I'm still looking for a help in investigating this issue. The problem appears on
two 7.4 boxes, while 7.3 are working OK. Ktrace shows, that indeed some of
sendto() calls on netgraph control socket are failing with EPERM:

  1246 mpd5     CALL  sendto(0x5,0x2886e020,0x98,0,0xbf7fc9b2,0x5)
  1246 mpd5     RET   sendto -1 errno 1 Operation not permitted

but few seconds later, sendto() called on the same socket succeeds:

  1246 mpd5     CALL  sendto(0x5,0x286487c0,0x38,0,0xbf9feae2,0x6)
  1246 mpd5     GIO   fd 5 wrote 56 bytes
       0x0000 0800 0000 0000 0000 0100 0000 0000 0000  |................|
       0x0010 b2b1 c600 1e51 c643 636d 6431 0000 0000  |.....Q.Ccmd1....|
       0x0020 0000 0000 0000 0000 0000 0000 0000 0000  |................|
       0x0030 0000 0000 0000 0000                      |........|

I looked at the netgraph code and I couldn't find any place where it returns EPERM.