CAPT OF ACR MLG ACFT OVERSHOT CLB ALT DUE TO DISTR OF ACFT EQUIP PROBLEM.

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I WAS FLYING AS CAPT ON ACR FLT NUMBER FROM MSY TO ATL. AN MLG TYPE ACFT. I WAS CLBING TO OUR ASSIGNED ALT OF FL230. NEAR FL180; HOU ATC TOLD US TO STOP CLBING AT FL200 BUT GAVE NO REASON. THE FO READ BACK THE CLRNC TO STOP THE CLB AT FL200. I AM NOT POSITIVE OF THE EXACT ALT WE WERE AT BUT I DO REMEMBER THAT WE WERE NOT GIVEN MUCH TIME TO REACT. AS THE FO WAS REACHING TO RESET THE ALT ALERT FROM THE PREVIOUS FL230 DOWN TO FL200; THE 2 RED MASTER WARNING LIGHTS ILLUMINATED. WE THEN LOOKED AT THE WARNING LIGHT PANEL TO SEE WHAT CAUSED THE MASTER WARNINGS AND SAW THE RED TAIL COMP TEMP HIGH LIGHT WAS ON. I HAD BEGUN TO LEVEL THE ACFT AND THE FO VERIFIED THAT I WAS AWARE OF THE TAIL COMPARTMENT PROBLEM. I DIRECTED HIM TO DO THE CHKLIST. AFTER WE SHUT DOWN THE SYSTEMS ACCORDING TO THE CHKLIST THE FO GOT THE ACFT HANDBOOK OUT OF HIS FLT KIT AND CHKED TO SEE THAT ALL AMPLIFICATIONS HAD BEEN COVERED. AS I WAS LISTENING TO THE FO READING THE PROCS HOU ATC ASKED TO VERIFY WE WERE AT FL200. I RECHKED MY ALTIMETER AND SAW THAT I LEVELED INDICATING FL204. I IMMEDIATELY AND RAPIDLY DSNDED TO FL200 LEAVING US ABOVE FL200 AT WHAT I WOULD ESTIMATE TO BE JUST SECONDS.