Samsung Side by Side (SRS614DW) Digital Temperature display LIES!!?

Our Sideby side fridge digital display has started always reading -18 for the freezer and 3 for the refrigerator, but the temperature inside of both keeps rising until water starts leaking out.
After a few hours, we have to shut the power off and on again - and then the actual (much higher) inside temperature displays on the LED display, after which it starts dropping again until it reaches the set -18 and 3, when it starts to rise again inside, while still reading -18 and 3 (and lying).
Any ideas what's going on here?

Sabina
July 2008