Corporate Meltdown is an Ultor mission that came with the Corporate Warfare DLC pack, available for Saints Row 2.
Briefing
The opening cutscene of this mission starts off with the Protagonist and Eric Gryphon arguing in the The Protagonist's personal room in the Saints' hideout about 'hurting' Dexter Jackson. The Protagonist complies that he does want to hurt Dex, though not fight the Masako, which he calls an "army". Gryphon answers that the Protagonist will have help, where The Protagonist questions why he gets "Ultor rent-a cops". The Protagonist also mentions that they're not shooting their own. Eric answers that they're not their own, and tells the Protagonist that Dex is moving radioactive waste from the nuclear plant that he can sell on the black market, and that he's thinking of using the Masako to clean up the evidence, and that IF Ultor find out what he's doing so, he's done for.
Mission
The point of the first part in the mission is to fill a nuclear truck with the radioactive waste located around the nuclear plant. While the truck is being filled, the player must defend the truck from incoming Masako. When the truck is filled for the first time, the player has to drive to the next pump(no incoming forces between the pumps), and face another army of Masako while the truck is being filled.
The second part of the mission you have to cover the trucks (being controlled by the AI) with a Tornado helicopter, while the trucks(and you) are being attacked by Masako in vehicles, Masako with Rocket Launchers on top of buildings, and sometimes, other helicopters.
Debriefing
The mission ends with a cutscene showing Dex at the airport with his assistant talking about what the assistant was ordered to do, and what Dexs true motives for going somewhere else is.