#1 typical problem is low air flow, due to a dirty filter (Change the filter and brush off the dry evaporator coil).
Dirt on the blower can also reduce airflow (clean the cupped blades of the blower with a brush).
Did the refrigerant leak ever get identified and fixed (sealed)? Low refrigerant will eventually lower the pressure in the evaporator, lowering the temperature if the condenser temperature is also low (on a cold morning). Good airflow will still move heat from the house into the evaporator and refrigerant, usually keeping it frost free, but this condition combined with even a slight reduction in airflow can produce the icing you experience.
The last simple thing to look for is closed vent grilles and registers. Winter heating tends to make some people close off vents to save on heating costs for vacant rooms. The furnace is not as sensitive to an airflow reduction as a cooling coil, it can operate reliably with less airflow, so make sure any closed registers are reopened each spring (probably the first thing you did when you found the no airflow problem).