cannot change primaryGroupID LDAP error 53

[steve]

Version 4.0.6-GIT-4bebda4
Hi
When trying to change the primaryGroupID for a user using wither 
ldbmodify or ldbedit:

failed to modify CN=dummy,CN=Users,DC=hh3,DC=site - LDAP error 53 
LDAP_UNWILLING_TO_PERFORM -  <error in module samldb: Unwilling to 
perform (53)> <>

The last time I needed to do it was in alpha 18 hwen it worked OK.

Any ideas?
Cheers,
Steve