samba - Aug 2004 - Refusing to create user that already exists

Help!
My Samba server keeps falling over with this in the winbind logs 
(USERNAME replaced):

[2004/08/12 14:54:02, 0] nsswitch/winbindd_acct.c:winbindd_create_user(884)
  winbindd_create_user: Refusing to create user that already exists 
(USERNAME)

Has anyone seen this?

Thanks
H