I'm not sure what you mean by "freezing up." If the unit runs constantly and will not cycle off, this can cause the refrigerator to freeze and the freezer to be extremely cold. This would indicate a problem with the cold control.
If the inside back panel of the freezer develops excessive frost and the unit experiences diminished cooling, you could have a problem with the automatic defrost system.
To help you diagnose and troubleshoot these types of problems (or even a different one), I need more details regarding your specific symptoms. Resubmit your question with additional details and we will be glad to help you with your refrigerator problem.