My bad, i should give you a explanation, a LEAK means the map is not enclosed properly(or have some entity outside in the void), for games like cod and counter strike, the map needs to be full enclosed by skybox in Radiant, not open to the void, its not something you need to reinstall everything to fix, just fix the geometry inside radiant and try again (the compiler even generates a pointfile to show where is leaking on the map), you can find more info here
https://developer.valvesoftware.com/wiki/Leak is for Source engine, but is very similar to cod