samba - Apr 2016 - Update from 3.5.10 to 3.6.23 broke cupsaddsmb

As an update to fix the badlock vulnerability I applied some updates to 
our (RHEL5-based) samba printer server last night, taking it from version 
0:3.5.10-0.109.el5_8 to 0:3.6.23-12.el5_11 (rpm package versions).

After this change attempts to add printer drivers with cupsaddsmb produced
errors of the form:

Running command: rpcclient localhost -N -A /tmp/cupsc7GVnF -c 'adddriver
"Windows NT x86"
"ini-director:pscript5.dll:ini-director.ppd:ps5ui.dll:pscript.hlp:NULL:RAW:p
script5.dll,ini-director.ppd,ps5ui.dll,pscript.hlp,pscript.ntf,cups6.ini,cup
sps6.dll,cupsui6.dll"'
cli_negprot: SMB signing is mandatory and the server doesn't support it.
failed negprot: NT_STATUS_ACCESS_DENIED
Cannot connect to server.  Error was NT_STATUS_ACCESS_DENIED

How can I fix this, please?  For the time being I've downgraded to the 
older version.

Thanks,

Owen

On Thu, 14 Apr 2016, Owen Dunn wrote:
> As an update to fix the badlock vulnerability I applied some updates to our
> (RHEL5-based) samba printer server last night, taking it from version 
> 0:3.5.10-0.109.el5_8 to 0:3.6.23-12.el5_11 (rpm package versions).
>
> After this change attempts to add printer drivers with cupsaddsmb produced
> errors of the form:
>
> Running command: rpcclient localhost -N -A /tmp/cupsc7GVnF -c
'adddriver
> "Windows NT x86"
>
"ini-director:pscript5.dll:ini-director.ppd:ps5ui.dll:pscript.hlp:NULL:RAW:p
>
script5.dll,ini-director.ppd,ps5ui.dll,pscript.hlp,pscript.ntf,cups6.ini,cup
> sps6.dll,cupsui6.dll"'
> cli_negprot: SMB signing is mandatory and the server doesn't support
it.
> failed negprot: NT_STATUS_ACCESS_DENIED
> Cannot connect to server.  Error was NT_STATUS_ACCESS_DENIED
>
> How can I fix this, please?  For the time being I've downgraded to the
older
> version.
Adding:

client ipc signing = auto

has fixed this problem for me.

Owen