on wl8.1 sp2 (W2000), using the default authenticator provider, when you remove
a member group first and then the parent group, you get an LDAP exception (see
below, both on the console as when manually contacting the ProviderMBean).

Is there a patch available for this problem?

It is probably due to the fact that the DefaultAuthenticatorImpl.removeGroup()
method removes the (child) group but not its memberships. when triing to remove
the parent, the list of children will contain non-existing children.
You can fix the illegal state by recreating the children and removing the parent

netscape.ldap.LDAPException: error result (32)
--------------- nested within: ------------------
weblogic.security.providers.authentication.LDAPAtn DelegateException: [Security:090260]Error
listing group members for t - with nested exception:
[netscape.ldap.LDAPException: error result (32)]
at weblogic.security.providers.authentication.LDAPAtn Delegate.listGroupMembers(LDAPAtnDelegate.java:118 8)
at weblogic.security.providers.authentication.LDAPAtn Delegate.removeGroup(LDAPAtnDelegate.java:1679)
at weblogic.security.providers.authentication.Default AuthenticatorImpl.removeGroup(DefaultAuthenticator Impl.java:236)