Can't print to secure printers with from MAC's

Did an upgrade from OES2 to OES11 SP1, have the Dec 12 2012 iPrint patches installed. Using MAC client V05.06.00. Will not print to any printers that are set as 'secure'. Prints to non-secure ones OK. Printing to a secure printer the job just sits on the MAC, does not enter the printer queue on the server.

Can't find any posts of others with similar problem. Any ideas on what else to check? What logs could check? Is this a bug?

Thanks for any help.

Colin.