ALT OVERSHOOT BY ACR MLG CAUSES LTSS WITH COMPANY ACFT.

Narrative

DURING AN ABNORMALLY BUSY TIME; WE DEPARTED IAH RWY 14L ON A RWY HDG; CLB TO 4000 FT. AFTER A LONGER THAN NORMAL RWY HDG CLRNC; WE WERE CLRED R TURN TO 250 DEGS; CLB AND MAINTAIN 5000. (NORMALLY; ON DEP FROM 14L SEBOUND THE CLRNC IS 'AFTER TKOF R TURN TO 250;' FOLLOWED BY A CLRNC TO 15000.) AFTER CLEAN UP THE CAPT WAS INVOLVED IN THE AFTER TKOF CHKLIST. DURING THIS TIME WE WERE GIVEN FURTHER A CLRNC TO 270 AND TA. THE 270 DEG HDG WAS PUZZLING SINCE OUR DEST WAS CRP. WHILE LOOKING FOR THE TFC; WE CLBED THROUGH 5000 FT AND GOT AN AURAL WARNING AT 5300 FT. WITH PWR AT IDLE AND AN IMMEDIATE NOSE OVER; WE RETURNED TO 5000 FT (MAX ALT WAS 5500 FT). DURING THAT DSCNT; WE CLRED TO A 190 DEG HDG. DURING THE MANEUVERING; I SAW A COMPANY ACFT TO THE R AND ABOVE US. I ESTIMATED ITS DISTANCE AT 2 MI. ATC SEEMS TO BE EXPERIENCING A HIGHER THAN USUAL; FOR LACK OF BETTER WORDS; 'STRESS LEVEL.' I BELIEVE THAT MORE STAFF MIGHT HAVE HELPED THAT PROBLEM. POSSIBLY; FEWER VECTORS; OR DELETING TA'S DURING HIGH WORKLOAD TIME WOULD HELP. WE AS A COMPANY MIGHT STRESS DOING THE AFTER TKOF CHKLIST ONCE THROUGH 10000 FT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CALLED TO CHK ON RPT STATUS AND INDICATED THAT THE FAA WAS TAKING ACTION ON HIS DEV DUE TO LTSS FROM COMPANY ACFT. RPTR NOT SURE OF OTHER ACFT TYPE AND INDICATED THAT ATC WAS VERY BUSY AS WAS THE FREQ. CTLR HAD CLRED TO 5000 FT AND RPTR HAD MINDSET ON 15000 AS IS USUALLY THE CLRNC GIVEN. ALT ALERTER DID ITS JOB; BUT NOT BEFORE SEPARATION WAS LOST.