1) take out MMC, and try again. 2) if it doesnt works, only hard resetting can help you. BUT you will lose ALL DATA on your phone... back up what u can using usb (if it is even possible), take out mmc and so on. To perform hard reset:
1. Turn off the LG KS-20 completely (do this by pressing and holding the power button and wait for the prompt).
2. Press and hold these three buttons–volume down, Call and power–till the LED (this is beside the front camera) flashes.
3. Release the buttons. That same LED should flash blue/red/green and power up.
4. The KS20 should be in a clean state.
NOTE, that, if your phone gets short on power (discharges) during resetting process, some bad things might happen. So, just connect it wih charger, then reset!