My house is about 4 years old, it has started to leak water into the basement surrounding the sewer pipe that leaves the basement. There is some kind of rubber boot around the sewer pipe that goes into the basement wall. There is no change of terrain outside the house and no sloping roof on that side. Any ideas?

You should be able to caulk the seal but it will last lonegr if it is bone dry when you apply the silicone.