A DOOR LIGHT WAS INCORRECTLY LISTED AND OPERATED AS AN MEL ITEM. THE ACTUAL PROB (AN UNSECURED PANEL) LED TO A RETURN LAND AS A RESULT OF AN INABILITY TO PRESSURIZE.

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OVERNIGHT ACFT CALLED IN EQUIP DOOR LIGHT 'ON.' WENT TO ACFT AND FOUND COMMON EQUIP DOOR OPEN; CLOSED DOOR CHKED WITH FLC IF LIGHT WAS OUT. CREW RESPONDED AFTER LOOKING AT OVERHEAD WITH THUMBS-UP INDICATING LIGHT WAS OUT. LATER CREW CALLED AGAIN SAYING LIGHT WAS 'ON' AGAIN. WENT TO ACFT AND REOPENED DOOR AND RECLOSED COMMON EQUIP DOOR. CREW INDICATED LIGHT STILL 'ON.' INSPECTED DOOR FOUND LATCHES TO BE OK. CALLED MAINT CTL FOR MEL. DOOR LIGHT PLACED ON MEL AS BEING INOP. ACFT DISPATCHED; CALLED BACK WITH PRESSURIZATION PROB; AND DECIDED TO RETURN TO IAH. AFTER INVESTIGATING; FOUND FORWARD E&E DOOR AJAR. MAINT CLOSED DOOR AFTER CHKING LATCHES; BOTH DOORS OPERATE SINGLE DOOR LIGHT. SUPPLEMENTAL INFO FROM ACN 312340: AT TKOF; FRONT E&E DOOR OPENED. NO PRESSURIZATION; AND EXTREME AIR FLOW NOISE IN COCKPIT. WE AIR RETURNED WITH ATC ASSISTANCE. I WAS UNABLE TO UNDERSTAND ATC INSTRUCTIONS BECAUSE OF NOISE LEVEL. WE WERE GIVEN 2000 FT. APPARENTLY I THOUGHT THE INSTRUCTIONS WERE TO MAINTAIN BELOW 2000 FT. WE WERE GIVEN 2 FREQ; AND 2 HDG CHANGES THAT WERE VERY DIFFICULT TO UNDERSTAND. LANDED BACK AT IAH OK.