My AC had stopped blowing from the vents and I checked it out and found the Cooling Coil frozen solid. Literally encased in ice. This is the first time it's done this and I let it melt for a few days and it worked again. Well the coil's freezin up again. How ca I prevent this from happening? Is it excess humidity? I'm in Georgia and I know it gets humid, but it's not been bad yet this year. The Thermostat stays about 75-77... thanks for any suggestions.