That is a fail.
You will want all cores functional for the duration of the test. 1 core failing may mean you need to increase your voltage however I would not recommend playing with voltage settings until you research what your cpu can handle, especially with an air cooler.
List the cpu and motherboard you have and I can probably provide better help.
I'm currently using an Asus P5E-VM HDMI mobo with a Core 2 Quad Q9450 cpu, with mutiplier at 8, FBS at 425@ 3.4GHz, I set up my cpu voltage in my BIOS at 1.45volts, not sure did I voltage too high.