I see you purchased the 3880 refillable carts and ConeColor ink in June 2013, and have purchased additional ink bottles since then.
Has the VM been working well since the carts were installed, until the other morning?
What is the physical ink level of the VM cart?
Did the VM cartridge recently run totally empty? (which would cause air to get into the internal ink lines, and interrupt ink flow)
Have you ever replaced parts, such as the dampers, wiper blade, capping station and/or print head?
Please let me know so I can help you past this and back to happily printing.
Best regards~ Dana