A320 FLT CREW DEPARTS FLL AND FLIES THE WRONG DEP.

Narrative

ON DEP FROM FLL; WE WERE ASSIGNED A HDG OF 090 DEGS FOR VECTORS TO THE THNDR TRANSITION. SUBSEQUENTLY; WE WERE ASSIGNED A HDG OF 300 DEGS TO INTERCEPT THE TRANSITION . THE FO (PF) ENGAGED THE NAV MODE AND AN INTERCEPT POINT WAS DISPLAYED ON THE NAV DISPLAY. WE INTERCEPTED THE 335 DEG RADIAL OF THE DHP VOR. AT THIS POINT; ATC ADVISED US THAT WE NEEDED TO TURN L TO 280 DEGS BECAUSE WE HAD INTERCEPTED THE ARKES TRANSITION. THE FO IMMEDIATELY TURNED OFF THE AUTOPLT AND EXECUTED A MANUAL HARD L TURN BACK TO A 280 DEG HDG. AT THIS POINT; WE REALIZED THAT OUR NAV DISPLAYS WERE OFF SIGNIFICANTLY SO REVERTED TO VOR NAV AND INTERCEPTED THE REAL 335 DEG RADIAL OF THE DHP VOR. WHAT IS SO DISTURBING ABOUT THIS INCIDENT IS THAT WE RECEIVED NO WARNING OF ANY TYPE THAT WE HAD A NAV ERROR. AFTER ABOUT 10 MINS OF FLT AND WELL AFTER THE INITIAL ERRONEOUS NAV ERROR; WE FINALLY DID RECEIVE FMGC MESSAGE TO CHK ACFT POS. THIS WAS THE FIRST WARNING WE RECEIVED THAT THERE WAS A PROB. ONCE WE FINALLY ESTABLISHED OURSELVES ON THE DEP USING VOR NAV AND WERE ABOVE ABOUT 12000 FT; WE WERE ABLE TO DETERMINE THAT THE FMGC'S WERE NOT RECEIVING RADIO UPDATING. THE NAV ERROR WAS AT THIS POINT APPROX 9 NM. THIS IS A RATHER LARGE ERROR FOR A TRIPE IRS EQUIPPED ACFT SO SHORTLY AFTER TKOF. WE CONTACTED ATC AND SOC AND CHANGED OUR EQUIP STATUS TO '/A' FOR THE REMAINDER OF THE FLT. MOC WAS ADVISED OF OUR PROB BUT OFFERED NO SOLUTION. I ENTERED THIS DISCREPANCY INTO THE ACFT LOGBOOK. AS FAR AS I NOW THERE WAS NO LOSS OF SEPARATION. UNFORTUNATELY; I STILL DO NOT HAVE ANY IDEA WHAT CAUSED THIS ERROR.