Most commonly, a leak in the inside unit is actually a stopped up drain line. You should check your drain line to make sure there are no clogs. First, locate your drain line. It is a PVC pipe that should come out of the ground near your outside unit. Hook a wet dry vacuum up to the drain line. That should clear a light restriction in the line.
With the vacuum hooked up, go back to your inside unit and locate the drain line access cap. It should be an offshoot of PVC from your drain line that has a cap on it. Remove the cap and run some fresh water through the line. The wet dry vacuum should clear the line completely at this point. If you are still experiencing water leakage than your drain pan could be rusted out or your inside coil is plugged. In either case you should call for service.