If your dehumidifier is freezing up then that actually means the unit itself is working well, and you probably just have the machine turned up too high for the current conditions.
Try turning down the setting on the unit so that it cycles on and off every few hours and does not run continuously.
Also try using some warm soapy water to clean off any dust or oily residue from the cooling coils in the rear of the unit. Remember to also clean the air intake filter while you are at it.
The ambient temperature in the room may also be a bit too low, so you can try adding some heat to the room if necessary. A dehumidifier will not work properly if the ambient air temperature is too low. Basically, the warmer and more humid the room is, the better they work. Since warm air rises, you can even try lifting the unit higher up off the cold floor onto a bench or table where the air is warmer.
You can click on the following link for a general operating and troubleshooting guide with additional tips on effective dehumidifier operation:
http://www.allergyconsumerreview.com/dehumidifier-advice-troubleshooting.html
And here is a link to a tip from another Expert (Heatman101) which includes his very detailed troubleshooting guide for dehumidifiers:
http://www.fixya.com/support/r4662409-dehumidifier_running_but_no_water_in
I hope that was helpful to you, good luck and take care.
If you choose to rate this solution, or Heatman 101's tip using the Thumbs Up scale provided, I thank you very much for your time and consideration.
Joe.