Honeywell RTH8500D Tstat

I hope that someone out there can help me. I have just purchased a new house and I wanted to make sure and swap out the cheap thermostats that came with it. I have installed the thermostat in both my upstairs unit and my downstairs unit. My downstairs works like a charm, but my upstairs is having serious issues. The major issue, is that the freon pipe freezes up all the way to the outside unit and even when I set it to 76 or 78. I am in atlanta and it has been in the mid-upper 80's which the A/C unit should handle.... It seems once that pipe freezes the air get less cool, but it should freeze so much. It freezes every day regardless of what temp it is set to. The 2nd issue and this is what leads me to belive there is something wrong, is that whether it is on heat or cool, I only get cool air? Any suggestions? I don't know a great deal about hvac, but I believe it is a single stage heat pump with no aux. I have my 170 set to 2 and my 190 set to 0. If I set 190 to 1 then I just get room temperature air. Please help me. I have spent so many hours trying to get this thing right. The most troubling issue is that the unit downstairs has the same settings, but no problems. Thanks in advance...