An A319 crew experienced a dual FMGC lockup in-flight. Normal functioning was restored after the crew completed the irregular procedure.

Narrative

The following information is filed about and pertains to this flight's partial loss of both FMGC's while enroute at cruise. For no apparent reason the Captain's and the First Officer's NAV displays went blank and both MCDU's froze; not accepting any inputs (although ACARS continued to work). The flight directors did not disappear and the autopilot did not disconnect. No ECAM appeared. I switched to Standby Navigation and informed ATC that we had lost RNAV capability and would require routing for standard navigation and was accommodated. The Co-pilot sent a message to Dispatch with the same information and sent a message to Maintenance with the problem. All other systems appeared normal. Maintenance suggested the resetting the FMGC's one at a time as outlined in the Irregualar procedure for both FMGC's failed (although not all the symptoms we had matched what was outlined in this procedure). The reset restored both NAV displays to their normal operation and both FMGC's to full function after a few minutes. We were in full VFR conditions the entire time and were expecting a visual approach on a almost cloudless day.