B777 First Officer reports track deviation on the TOMO WEST 2 departure from RJBB. While the autopilot is tracking to the first fix at D10.5 KNE the aircraft suddenly makes a right turn which is quickly corrected by the flying pilot.

Narrative

On the TOMO West 2 departure; with the autopilot engaged; the aircraft suddenly turned right while tracking out the 270 radial off of KNE (which was on the departure procedure). The Captain immediately changed to heading mode and pointed the aircraft at the KNE 10.5 DME fix trying to get the aircraft back on course. During the initial aircraft turn off course; the magenta line disappeared from the Navigation Display (FMS generated). The Captain tried to regain the FMS navigation course but within seconds of our first correction back to course; ATC asked us if we were flying the correct departure and we advised them that we had lost our navigation solution and that we were trying to regain it. ATC offered us a heading and we accepted the heading. We then were able to regain FMS navigational cues about 30 seconds later at the most. The departure was briefed and verified prior to departure and the FMS and the navigation display were cross checked with no apparent issues prior to departure. We were unable to figure out why the aircraft turned off course; but we were able to begin the correction back towards course because situational awareness had not been lost. It can also be noted that we are new to this aircraft. Further; with reduced training budgets; crews are entering line service with minimum systems knowledge requiring additional time to correct such problems.