Data upload trouble with 332c

I have a Lowrance 332c and I had problems with the unit and returned it to Lowarance for warrenty work. They replaced the unit fine but I am having trouble loading my waypoints and trails on the new unit. I saved the data from my old unit to a sd card and I can upload it to the new unit fine but when I take the SD card out the data is not saved on the the units memory. I uploaded my SD card to my buddies unit and it worked just fine. I can take the sd card out my buddies unit and the waypoints and trails are there. Do I need to send this unit back to Lowrance or am I doing something wrong.

Thanks in advance

Bow