B757-200 CREW HAD THE COMPANY FLT PLANNING COMPUTER CHANGE THE PRE-DEP CLRNC ROUTING WITHOUT INFORMING THE CREW.

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OUR RELEASE CALLED FOR 1 RTE TO BE FLOWN. WHEN WE GOT THE PDC; IT SHOWED NO REVISED SEGMENT. WHEN WE FLEW THE RTE; ORD CTR SAID; 'WHERE ARE YOU GOING;' AFTER WE MADE A PLANNED TURN AT BAE TO DLL. WE SAID WE WERE FLYING THE FLT PLAN. AFTER TAKING A CLOSER LOOK AT THE PDC; IT SHOWED THE FILED RTE AS SOMETHING DIFFERENT THAN RELEASE #1; WHICH WAS STILL CURRENT. WE GOT THE REROUTE FROM ATC WITHOUT INCIDENT. AFTER TALKING TO DISPATCH; THEY SAID A COMPUTER GLITCH HAD OCCURRED AND WOULD BE INVESTIGATED. SUPPLEMENTAL INFO FROM ACN 589467: WE WERE FOLLOWING OUR PRINTED PDC ORIGINALLY ISSUED PRIOR TO TKOF; WHICH ALSO STATED 'NO REVISED ROUTING.' OUR DISPATCHER TOLD US THAT THERE WAS A COMPUTER GLITCH AND THAT THE CHANGE OF ROUTING WASN'T ABLE TO GET TO US OR HIM IN TIME AND EVEN THOUGH ATC KNEW OF IT; DUE TO THE COMPUTER GLITCH; WE WERE ISSUED A PDC WITH NO ROUTING CHANGES. SUPPLEMENTAL INFO FROM ACN 589466: PROGRAM SENT AIRWAYS BASED ON THE RTE IN THE COMPUTER AT THAT TIME. I CAME BACK TO IT 8 MINS LATER; SENT RELEASE AND RELEASE WENT OUT WITH A DIFFERENT RTE. CAPT NOTICED DIFFERENCE IN FILED AIRWAYS VERSUS FLT PLAN; PROGRAMMING CHANGE IS REQUIRED THAT WILL NOT ALLOW AIRWAYS TO BE SENT WHEN ENRTE WT IS EXCEEDED.