LOSS OF SEPARATION BTWN MD88 AND AN UNKNOWN ACFT ASSIGNED THE SAME ALT WITHOUT APPROPRIATE LATERAL SEPARATION.

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ON VECTORS ON ILS RWY 27 CVG ON RADAR R DOWNWIND. THERE WAS RADIO CHATTER BTWN A FLT SOMEWHERE AHEAD IN THE SEQUENCE THAT HAD NOT TURNED TO THE ASSIGNED HEADING AS QUICKLY AS THE CTLR EXPECTED. THERE WAS QUITE A BIT OF COM BTWN THIS FLT AND ATC. DURING THAT PERIOD WE WERE GIVEN ANOTHER HEADING TO BASE LEG AND CLRED OUT OF 7000 FT TO 5000 FT. LATER WE WERE ISSUED AN INTERCEPT HEADING; AND DSNDING OUT OF 5500 FT; WE RECEIVED A TCASII 'TFC;' NOTING A TARGET APPROX 2-3 MI IN TRAIL AT 5000 FT. THE CTLR CALLED TO SAY WE WERE SUPPOSED TO BE AT 6000 FT. THE CAPT (PNF) ASKED IF WE SHOULD CLB BACK TO 6000 FT. ATC SAID NO AND CLRED US FOR THE ILS (WE STAYED 500 FT ABOVE THE TCASII TARGET UNTIL YELLOW DISAPPEARED). AS PER COMPANY PROCS; WHEN ASSIGNED A NEW ALT; IT IS SET IN THE ALT SELECT AND THEN BOTH PLTS POINT TO IT AND SAY THE ALT. FOR THIS REASON I WAS 100% CERTAIN WE WERE ASSIGNED 5000 FT. AFTER LNDG THE CAPT PHONED THE APCH CTL SUPVR WHO HAD JUST REVIEWED THE TAPES. THE SUPVR CONFIRMED WE HAD BEEN CLRED TO 5000 FT. IT IS MY OPINION THAT THE EXTRANEOUS COM BTWN THE PRECEDING ACFT (WHICH HAD APPARENTLY TURNED THE 'LONG WAY' TO ITS ASSIGNED HEADING AND ENDED UP BEHIND US) AND APCH HAD DISTRACTED THE CTLR. PERHAPS IT WOULD HAVE BEEN BEST TO JUST GET ON WITH BUSINESS AND THEN TALK IT OVER ON THE PHONE AFTER LNDG. NOTE: THE TCASII TA ADVISORY OCCURRED PRIOR TO THE CTLR QUESTIONING OUR ALT.