If things freeze the temperature at the bottom must be close to 0 °C then.
The variations of mechanism overrun, small inaccuracy of the thermostat and the temperature gradient inside the box may all add together to cause this.
Blood freezes at -2 °C so the bottom of your fridge may even be below zero.
Some cove on wikipedia writes...
"...generally 2 to 8 °C (36 to 46 °F) is ideal for the refrigerator compartment and -18 °C (0 °F) for the freezer."
You might put the setting to 5 °C and see how things go.
Stay cool...
Peccavi, January 2009
