B767-300 First Officer reports a track deviation during the the EVX departure from Runway 9R at LFPG.

Narrative

A very thorough takeoff and departure briefing was given to me and thr Relief Pilot at the gate. We were cleared into position on Runway 9R. I verified my scale and that the aircraft symbol was on the runway. The Captain made a normal takeoff and was climbing as per the Evreux departure profile. About 1;000 FT the Captain called for an autopilot which I selected but it did not engage and we received a master warning. I reselected a different autopilot and it engaged. It was at this time that I noticed the runway/magenta line was off to the left. The SID calls for straight out to 8.5 DME. We didn't turn prior to the autopilot being engaged but now that it was on the aircraft started a small turn to the left. Departure asked us twice to verify we were on the correct departure which we agreed we were. 8.5 DME came up quick and we started our left turn as per the procedure. Once we were well established in to our flight we discussed what happened. A map shift is the only logical answer we could come up with.