A CRJ200 FMS FAILED TO UPDATE AFTER TKOF. A 'DR EXCESS 5 MIN' ANNUNCIATED AFTER THE CREW WAS UNABLE TO NAVIGATE TO A FIX ON THE ROUTE. THE FMS WAS ABOUT 100 NM OFF COURSE.

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WE DEPARTED RWY 13R WITH A CLB TO 5000 FT AND A HDG OF 170 DEGS. AFTER WE WERE ESTABLISHED ON A 170 DEG HDG WE WERE TOLD TO TURN L TO INTXN. OUR FMS SHOWED INTXN TO OUR R. WE QUERIED ATC TO CONFIRM THE L TURN. THE CTLR SAID; 'CLRED DIRECT INTXN.' WE SET INTXN IN THE FMS AND TURNED R. ATC THEN ASKED IF WE WERE IN A R TURN AND OF COURSE WE WERE. ATC TOLD US TO TURN L TO A PARTICULAR HDG (150 DEGS; I THINK) AND WE RECEIVED MORE VECTORS TO GET TO A HDG IN THE DIRECTION OF INTXN. DURING THE VECTORS; WE NOTICED 'DR EXCESS 5 MINS' ON THE FMS. WE DID NOT SEE THIS MESSAGE WAS INOP AND WE SWITCHED TO GREEN DATA AND NAV'ED USING VOR'S. THE DISTANCE BTWN WWW AND YYY IS LARGE AND WE NEEDED SOME VECTORS AS HELP TO STAY ON COURSE. WE NAV'ED FOR THE REMAINDER OF THE FLT ON GREEN DATA WITH THE USE OF ENRTE CHARTS AND VECTORS. THE REMAINDER OF THE FLT PROCEEDED WITHOUT EVENT. I WROTE UP THE FMS IN ZZZ1. THE MAINT MAN HAD TROUBLE GETTING THE FMS TO UPDATE ITS POS. THAT SEEMS TO BE THE PROB WITH THE FMS. AFTER SEVERAL TRIES AND ON RESET; THE FMS FINALLY UPDATED ITS POS AND THE MAINT MAN SIGNED OFF ON THE WRITE-UP. DURING PREFLT AT ZZZ WE PROGRAMMED THE FMS PROPERLY AND WE BOTH CONFIRMED THE FLT PLAN. NO MESSAGES WERE SHOWING ON THE FMS. THE TOGA BUTTONS WERE ENGAGED BEFORE TKOF AND NO MESSAGES WERE DISPLAYED DURING TKOF AND CLB. ONCE THE MESSAGES WERE DISPLAYED WE NOTICED THAT THE FMS WAS SHOWING ABOUT 100 NM OFF COURSE (TO THE N) FOR THE ENTIRE FLT. THAT'S WHY INTXN WAS SHOWN TO OUR R AND NOT TO OUR L. AS A CREW; WE COULD HAVE DISPLAYED BETTER SITUATIONAL AWARENESS. THE DEP CHART CLEARLY SHOWED INTXN WOULD HAVE BEEN TO OUR L AFTER A TURN TO 170 DEGS. WE RELIED TOO HEAVILY ON THE FMS FOR NAV INFO.