2 year old system freezing up?

[nascarfamily]

About 3 weeks ago, while going through a hot spell, our 2 year old central air system froze up. No problem, figured it was the filter I'd forgotten to change - replaced it, AC worked fine. Yesterday it started getting very warm and humid outside again; by the time I turned the AC on, it was 82 degrees in the house. By morning, the house had cooled to the set temperature, but the condensor was running constantly and no air was coming from the vents again. Yep, froze up again. Checked the filter, and all the parts to make sure everything looks clean, and it does. All the vents are open in the house, so I assume it's not an air flow problem? So, this leads me to the question - is low freon pretty much the only other cause? How does a 2 year old system lose freon that quickly?

[DNT1]

Probably a small leak but check the evaporator coil closely sometimes a badly installed return air duct can leak in dirt and debris behind the filter and the garbage will build up on the inlet side of the coil and slow the airflow. I assume that you are using a free flowing return air filter, not one of the pleated ones? If the coil is clean and you have installed a free flowing filter you have done about all a HO could do without the proper training/ EPA certification and some specialized equipment.

[hiltontech]

Coming from your outside unit you will see two copper lines, the larger one should be cold and wet while the smaller one warm, if the large line isn't cold and wet than there is a chance you have a leak and have lost some for your freon, you would have to call out a tech to check your charge though being you have to be EPA certified.
If you haven't been changing your filters as you should have in the last 3 years than the coils could be dirty even though the unit is only 3 years old.
Again, my guess is that your low on freon, if you are have them repair it before charging it back up.