Our A/C system is about one year old. The unit outside is running (fan turning) and the air handler in the attic is running. But the vents have very little air coming out. The air that is coming out is cold, but you can barely feel it. I checked the duct work and couldn't find any problems, leaks, etc. Any ideas?

If you have a air flow restriction or if your system is low on refrigerant, the evaporator coil will start to frost over blocking the air flow. Check your return air filters for air flow restriction. A system that is less than one year old has a lot of warranty left on it. Your installation company should be willing to help you out.