Gutters should extend past the roof line a couple of inches to catch the rain water coming off the edge of the roof instead of running down the side of your home.
If you have this problem it may be because the gutter is lined up with the roof line. Water then tends to flow over the gutter end cap, down the gutters, to the fascia and soffit with possible water damage as a result.
More often than not, the gutters are not positioned properly at the ends of the run. Call the installer have him correct the problem, making sure to position the gutters to go past the roof line.