E145 FLT CREW DEVIATED FROM RNAV SID TRACK AT DFW WHEN FMS SYSTEMS UNABLE TO DEAL WITH XWIND.

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RNAV DEP AT NIGHT OFF RWY 36R AT DFW. AFTER DEP AT APPROX 1200 FT MSL USING THE FMS; COMMAND BARS ARE INDICATING A R TURN WITH APPROXIMATE 5 DEGS OF BANK. FOLLOWING THE COMMAND BARS KEEPS THE CDI PERFECTLY CENTERED. I CHKED THE WIND TO SEE WHY A R TURN WAS BEING DISPLAYED. FMS SHOWED 42 KTS OF XWIND FROM THE 2 O'CLOCK POSITION. WE CONTINUED TO FOLLOW COMMAND BARS WITH CDI PERFECTLY CENTERED. ATC QUERIED WHETHER WE SHOW OURSELVES ON COURSE. I REPLIED AFFIRMATIVE. ATC REPLIED; 'I SHOW YOU R OF COURSE; TURN L TO HDG 330.' FO WAS THE PF WHO COMPLIED WITH ATC'S INSTRUCTIONS. AS WE MADE THE L TURN; THE CDI CORRECTED BACK TO THE L AND THE WIND SPD AND DIRECTION INDICATED ON THE MFD WAS 7 KTS FROM OUR 2 O'CLOCK POSITION. FROM THE COCKPIT INSTRUMENTS THE MAXIMUM DEVIATION WAS 1/2 TO 1 DOT RIGHT OF COURSE AND THAT OCCURRED ONLY AFTER WE BEGAN OUR TURN TO THE ATC HDG OF 330 DEGS. THE REMAINDER OF THE FLT WAS UNEVENTFUL AND PROVIDED NO INDICATION OF INSTRUMENT ERROR DURING THE REMAINDER OF THE FLT. THE FMS WAS PROPERLY PROGRAMMED WITH NO ABNORMAL/ERROR MESSAGES DISPLAYED.