How do I fix my multimeter, which doesn't seem able to measure resistance?

I've got a Caltek CM1200 multimeter, which I bought ages ago. http://www.caltek.com.hk/cm1200.htm

It can measure voltage perfectly. I'm pretty sure the battery works, as it displays 0 when you go to a voltage with nothing connected to the probes.

When I move the dial to the resistance measuring area, the display shows nothing. Completely blank (I expect something meaning infinite).

If I connect the two probes (plugged into the bottom two sockets, marked V/Ohm/mA and COM) to each other, it is still blank (I expect zero).

What is wrong with my multimeter, or am I missing something at how to measure resistance?