B737-300 IN IMC UNDER AFDS CTL GETS OFF THE LOC AND NEVER RECOVERS. FLC FAILS TO TAKE CTL AND RECOVER. THEY ARE FINALLY CLRED FOR A VISUAL APCH TO A PARALLEL RWY ON THE FAR SIDE OF THE ARPT.

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DEN APCH CLRED US TO MAINTAIN 210 KTS; 040 DEG HDG TO INTERCEPT ILS RWY 35L LOC; CLRED FOR APCH. CAPT THEN ARMED THE AUTOPLT/FLT DIRECTOR (AFDS) TO CAPTURE THE LOC AND GS. WITH THE HIGH GND SPD AND GREATER THAN NORMAL INTERCEPT ANGLE THE AFDS CAPTURED THE LOC; FLEW THROUGH THE COURSE MAKING THE L TURN TO GET BACK ON COURSE. ATC (APCH) ASKED US TO MAINTAIN 190 KTS. (I BELIEVE THIS WAS THE CLRNC) TO DYMON; THE OM (6.6 DME). THE AFDS ROLLED OUT ON A 335-340 DEG HDG TO GET BACK ON COURSE. THE ACFT FLEW THROUGH THE COURSE NWBOUND AND FAILED TO TURN TO TRACK INBOUND. I BROUGHT THIS TO THE CAPT'S ATTN AT WHICH TIME HE TRIED TO GET THE ACFT BACK ON COURSE USING THE AFDS. ATC CLRED US TO A LOWER ALT AND SHORTLY AFTER TOLD US WE WERE L OF COURSE AND TO TURN R TO INTERCEPT. THE CAPT HAD STILL NOT DISENGAGED THE AFDS AND HE WAS NOW PARALLELING THE LOC AND DSNDING. ATC STARTED TO GIVE US MISSED APCH INSTRUCTIONS L TURN 260 DEGS CLB AND MAINTAIN 8000 FT OR 9000 FT? (CAN'T REMEMBER) AND IN SAME BREATH ASKED IF WE COULD REINTERCEPT AND CONTINUE APCH? THE CAPT DISENGAGED AUTOPLT AND SAID THAT WE COULD CONTINUE. APCH TOLD US TO TURN R (CAPT IS STILL PARALLELING COURSE; I HAVE REMINDED HIM OF THIS 3-4 TIMES NOW) AND CONTACT TWR. TWR CLRED US TO LAND RWY 35L AND ASKED IF WE WERE TURNING TO REGAIN COURSE. AROUND THIS TIME WE HAD ACQUIRED VISUAL REF WITH THE TERRAIN AND IDENTIFIABLE PORTIONS OF ARPT (PARKING LOTS; TERMINAL; TWR). TWR ASKED IF WE HAD RWY 35L IN SIGHT. WE DID NOT AND STATED SO. TWR ASKED IF WE HAD RWY 34 IN SIGHT. WE DID HAVE RWY 34 IN SIGHT AND TWR THEN CLRED US TO LAND ON RWY 34. CONTRIBUTING FACTORS TO THIS WAS APCH HIGH SPD/LARGE INTERCEPT ANGLE; CAPT'S FAILURE TO DISENGAGE AFDS AND FLY MANUALLY; MY FAILURE TO GET CAPT'S ATTN TO TURN FURTHER R; FAILURE OF APCH CTL ASKING US IF WE CAN MAKE IT RIGHT AFTER THE MISSED CLRNC. I THINK THEY SHOULD HAVE MADE US MISS. AFTER THAT CLRNC WE THOUGHT THAT WE COULD REINTERCEPT AND WE COULD HAVE HAD WE BEEN AGGRESSIVE ENOUGH TO GET BACK ON COURSE. FAILURE ON TRAINING. NOT ENOUGH ON AFDS/FMC; TURNING IT OFF AND FLYING MANUALLY NEVER EMPHASIZED ENOUGH. WHAT STARTED OUT AS A PRECISION APCH AND FINISHED AS A NON PRECISION/VISUAL APCH SHOULD NEVER HAPPEN. AUTOPLT WAS TESTED ELECTRONICALLY ON THE GND WITH NO FAULTS DETECTED. NOTE: WE HAD GONE ABOVE GLIDE PATH (RWY 35L) AT SOME POINT NEVER TO REGAIN IT AND DID NOT USE EXCESSIVE (MORE THAN 1200 FPM) DSCNT RATES TO RE-ESTABLISH IT.