A tardy response to the Flight Crew's request for maintenance on a faulty cowling latch contributes to accepting a clearance for pushback with a maintenance crew on a lift at the forward cargo door.

Narrative

On return from the Walk-around the First Officer thought one cowling latch MIGHT be loose on the right engine. We called maintenance approximately thirty-five minutes before departure; but did not send a computer maintenance code. After fifteen minutes passed we had heard nothing back from Maintenance; and decided we were probably in error by not sending in an computer maintenance code on the cowling latch. It was now 20 min prior to departure time; we followed up the computer maintenance code with a radio call to maintenance. After another ten minutes we still had not received a new maintenance release and I again radioed maintenance that the agent was getting ready to close the door; and that we needed the maintenance release. Finally at ten minutes past scheduled departure; we saw the maintenance release rolling off the printer. We then called ramp tower for pushback. Ramp tower cleared us to push. Per SOP; the tug crew cleared us to release brakes. At that point The First Officer said he saw a mechanic on a lift near the forward cargo door in the reflection of the terminal windows. The tug crew never mentioned seeing him at all. I immediately canceled the pushback over the interphone and reset the brakes. We had never moved but it was way too close. Communication external to the cockpit broke down very badly; I'm not sure why the push-crew never saw the mechanic on a lift up to the airplane; I also don't understand why it took over 30 min to receive a new maintenance release for a simple cowling latch check; in spite of repeated radio calls about needing a new maintenance release. As for my part as the Captain; I should have advocated to the First Officer more forcefully the need to always send a computer maintenance code when contacting maintenance.