hi, you may have the same problem as I with my old philips match///line tv, model:29sx8876/93b[made in singapore]. I solved the "lock" problem by doing the following steps:
1. press "Feather" button, on the bottom-left of your remote control. by doing this, you should see "Feather" menu displayed on your TV.
2. using the arrow button set to navigate to the lock menu, the last menu item (at the bottom), press right arrow button twice time to change menu value, to OFF.
Now, I press the Install button on the top of TV, to call out search channel menu. .... operate the menu by using the arrow button set on your TV remote control.
hopefully this will help you out.....
jack@china, August 2008