re: AC Repair Companies...who could I get out on a Sunday?

Is your filter clean? First question you'll get. Seriously, is it? Your compressor is running, otherwise the line wouldn't freeze. Like someone stated above, you have one of two issues....insufficient airflow (dirty filter, dirty evaporator coil, dirty condenser coil or a motor out) or you're low on refrigerant and have a possible leak.

Turn on your "fan" only on the tstat to de-ice the system. Do not put the system into cooling mode. If you haven't changed your filter in months (or years), change it and see what happens.

Also, just so you know, when you see your line frozen outside, that means the evaporator coil in your attic or closet is a solid block of ice, too. You need to run the system in the fan mode to melt that block of ice to get the airflow again.