TRACON DEP CTLR BECOMES INVOLVED IN A SYS ERROR WITH AN E120 ON AN IFR DEP; AN ACR B737 ON A MISSED APCH; AND A TRANSITING BE35; MOST LIKELY VFR. THE E120 WAS TOLD TO EXPECT VECTOR UNDER AND AROUND THE B737. THE B737 TOOK THE E120'S VECTORS. THE E120 INITIATED EVASIVE MSAW ACTION DUE TO APCHING TERRAIN; AND RECEIVED A TCASII ALERT WITH THE BE35 DURING THE MSAW MANEUVER.

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AS WE DEPARTED RWY 24L AT LAX; AN ACR Y JET DECLARED A GAR ON RWY 24R. THEY WERE GIVEN A HDG OF 270 DEGS AND WE WERE TOLD TO OFFSET TO THE L. WE WERE THEN TOLD TO MAINTAIN 2000 FT AND CONTACT DEP ON 125.2. DEP TOLD US TO CLB TO 3000 FT AND EXPECT TO BE VECTORED UNDER THE ACR Y WHICH WE HAD IN SIGHT. AFTER ACR Y CLBED ABOVE OUR ALT; WE WERE GIVEN A VECTOR OF 360 DEGS UNDER THEM. I COMMENTED TO THE CAPT WE COULD NOT STAY ON THIS HDG LONG BECAUSE OF TERRAIN. AS WE APCHED THE HIGHER TERRAIN; A HDG WAS ISSUED; BUT THERE WAS CONFUSION ON THE FREQ AS TO WHO IT WAS TO. NEITHER THE CAPT NOR I REMEMBERED HEARING A VECTOR FOR US; BUT SUSPECTED IT WAS FOR US. FOR AT LEAST 1 MIN; THE FREQ WAS USELESS WITH SOCAL APCH CTL; ACR Y JET AND OTHERS BLOCKING EACH OTHER. ABOUT THE SAME TIME I WAS GETTING NERVOUS ABOUT TERRAIN; WE GOT A TCASII TFC ALERT. OFF OUR L SIDE WE BOTH SPOTTED A SMALLER GA ACFT (ACFT Z) AT OUR ALT. UNABLE TO TURN L BECAUSE OF TFC; R BECAUSE ACR Y WAS SOMEWHERE OVER THERE AND NOW TURNING OUR WAY BECAUSE WE FIGURED OUT HE OR SHE TOOK OUR VECTOR. I INITIATED A CLB TO AVOID TERRAIN. I CLBED TO 3800 FT. SOCAL NOTICED OUR ALTDEV AND INSTRUCTED US TO DSND TO 3000 FT. THE CAPT INFORMED THE CTLR WE HAD CLBED DUE TO TERRAIN; WERE CLR OF IT AND COULD NOW DSND BACK TO 3000 FT. THE ACR Y JET WAS NOW BACK IN SIGHT. WE GOT ANOTHER TCASII ALERT; BUT NEVER SAW ADDITIONAL TFC. I THINK IT MIGHT HAVE BEEN ACR Y; BUT AM NOT SURE. THIS WHOLE SIT COULD HAVE BEEN AVOIDED IF THE CTLR WOULD HAVE TAKEN CTL OF THE FREQ AND ASKED EVERYBODY TO 'STAND BY;' THEN ISSUED SPECIFIC INSTRUCTIONS. ACR Y ALSO SHOULD HAVE LISTENED MORE CAREFULLY WHEN THEY TOOK THE WRONG CALL. THEY BLOCKED THE FREQ AT LEAST 3 TIMES ASKING WHAT HDG TO FLY WHEN SOCAL APCH CTL WAS TRYING TO STRAIGHTEN THINGS OUT. SUPPLEMENTAL INFO FROM ACN 413889: MY FO CLBED TO 3800 FT; AND I WAS UNABLE TO NOTIFY OUR SIT WITH ATC DUE TO HIGH FREQ CONGESTION. ACR Y HAD A SIMILAR SOUNDING CALL SIGN. WE LATER FOUND OUT THAT THE MVA FOR OUR AREA WAS 3900 FT.