A320 FLC HAS ALTDEV DURING STAR INTO KLAX.

Narrative

CAPT -- PNF; FO -- PF. WE WERE ON ARR TO LAX WITH PARADISE ARR RWY 25L SET IN MCDU. APCH GIVES US 'RWY 24R' AND CLRS US FOR THE PARADISE ARR; COMPLY WITH ALL THE ALT RESTRS. RWY 24R WITH THE PARADISE ARR WAS SET-UP IN THE SECONDARY FLT PLAN. SECONDARY WAS ACTIVATED. MANY OF THE FIXES ON THE ARR DISAPPEARED. I TRIED TO RE-INSTALL THE ARR; BUT FAILED TO GET IT IN BEFORE THE APCH CTLR TOLD US TO LEVEL OFF. WE WERE R OF COURSE AND AT ABOUT 9500 FT. I EXPLAINED THE SIT AND THE CTLR VECTORED US TO RWY 24R. WHEN ON THE GND AND THINGS SLOWED DOWN; I REALIZED WHAT THE PROB HAD TO BE. NORMALLY; THE SAME ARR REMAINS WHEN CHANGING RWYS IN THE FLT PLAN. WITH THE PARADISE ARR; IT HAS TO BE RESELECTED EACH TIME. WHEN I PUT RWY 24R IN THE SECONDARY; I MUST HAVE OVERLOOKED THIS DIFFERENCE. THIS IS THE ONLY THING THAT MAKES SENSE. WHEN I PUT IT IN THE SECONDARY; I HAD BEEN DISTR BY OTHER EVENTS; AND THIS CAUSED THE ERROR TO BE OVERLOOKED. PRIMARY WAS COPIED TO THE SECONDARY PRIOR TO SELECTING RWY 24R IN THE SECONDARY. THE CTLR; WHEN I ASKED IF I NEEDED TO CALL HIM WHEN ON THE GND; SAID; 'NO;' EVERYTHING HAD BEEN TAKEN CARE OF. EVERYTHING WAS ALRIGHT.