BIG ALT BUST.

Narrative

PRIOR TO DEPARTING PROVIDENCE; I WAS INVOLVED IN A SIT PRIOR TO BOARDING THE ACFT IN WHICH I CHASTISED THE CABIN CREW FOR FAILING TO GET THE CABIN PREPARED FOR BOARDING. THIS EVENT WAS WEIGHING HEAVILY ON MY MIND AS WE DEPARTED PROVIDENCE. UPON REACHING CRUISE ALT; I INSTIGATED A DISCUSSION WITH MY FO AND WE BEGAN TO CONVERSE ON THE SUBJECT. WE WERE GIVEN A CLRNC TO CROSS 25 MI N OF SPARTA AT 25 DME WHICH I ACKNOWLEDGED. THE FO SET THE XING RESTR ON THE FMS; BUT; DUE TO THE DISTR CREATED BY THE (MY) CONVERSATION; I CAN ONLY ASSUME THAT IT WAS NOT PROPERLY SET. SOME TIME LATER; WE WERE QUERIED BY ATC AS TO OUR ALT AND WE REALIZED WE HAD FAILED TO START OUR DSCNT IN TIME TO MAKE THE XING RESTR. FMS WAS SELECTED TO LEVEL CHANGE AND ATC ISSUED A L 360 DEG TURN TO REINTERCEPT THE AIRWAY AND DSND TO 7000 FT. WE WERE PASSING 13200 FT AT THE TIME OF THE INCIDENT AND; DUE TO THE DISTR OF THE CONVERSATION; I FAILED TO NOTE THE FMS SETUP THAT LED TO THE FAILURE TO MAKE THE XING RESTR. WHAT CAUSED THIS PROB WAS MY FAILURE TO DISCIPLINE MYSELF IN ALLOWING AN OUTSIDE DISTR TO TAKE PRECEDENT OVER THE OP OF THE ACFT. SUPPLEMENTAL INFO FROM ACN 265323: I WAS DISTRACTED BY THE CAPT'S CONVERSATION AND WE BOTH FAILED TO MONITOR THE AIRPLANE'S DSCNT. I ESTIMATE THAT WE CROSSED THE FIX AT AROUND 13000 FT MSL. FOR SOME UNKNOWN REASON; VNAV ON THE COMPUTER; NEVER CAPTURED THE ACFT PATH DSCNT.