OK, I have the following in my Shooting Menu 4: LV Func.
Live View Shoot. Enabled
AF Mode. Live Mode
Grid Display. 3x3
Aspect Ratio. 3:2
Expo Simulation. Enabled
Silent LV Shoot. Mode 1
Metering Timer. 16sec
Note that the autofocus in live view is significantly slower and will not lock unless you are very still (on a tripod). Either you could are perhaps being impatient (It can take several seconds to focus depending upon the lens!), or you are not getting a fixed point to focus on. The slightest movement will occasion the camera to continue hunting in LV.