Just recently replaced 3 x HP Laserjet 1320's with 3 x HP Laserjet Pro 400 M401dn.
Since doing so we are getting Error 21 - Page too complex errors. This is happening only on specific PDF attachments from Microsoft Outlook. I can print the emails out too 1 of the HP Laserjet 1320's mentioned above and to a HP Officejet L7780 with no issues.
I have also now updated the firmware to 20130415 with no joy.
Any one have any ideas what's causing this slightly frustrating problem ?