How to disable frontscreen keys on LG 8100?

As our LG 8100 phones bounce around in my pocket and in my wife's purse, the frontscreen and side buttons are constantly being activated. Our phones keep recording blank photos and videos. There must be a way to disable these outside buttons, but I can't figure it out. Any tips?

Read your user's guide to lock the keypad.
My phone (i880) it's: menue *

To lock the phone you simply press and hold the "#" key for a couple of seconds. To unlock the phone, you will need the passcode (usually the last 4 digits of your mobile number. It should be noted that the front screen keys generally don't do anything unless you have the music player turned on. The side keys, on the other hand, are always active.

Thanks camstuf and paulcman. All set.