My 15" 1.67Ghz Power book refuses to sleep when i close the lid. Its as though i did nothing, even the Apple logo at the back remains lit.

If i go into the Apple menu and put it to sleep from there that's fine and it goes to sleep, display goes off and the pulsing light comes on.

Did you check the power settings in OSX?

Just a guess, but the sensor is probably in the hinge and replacing the entire hinge might be required if this problem is constant, not something that comes and goes. IIRC, I had that problem on my first Titanium PowerBook (first Mac I ever owned), but it would sometimes work and other times it would not. Since you can put it to sleep with the menu item, I would not bother trying to fix it by replacing the hinge, as it will not be cheap and may not be easy. My first PowerBook died a few times before I gave up on fixing it and moved on to an Intel MacBook, but now the MacBook has been given to my 17 year old Son and I am back on a G4 PowerBook (1.67GHz 17-inch model).

@Pampers - Yes all the settings are good

@amigadave - Yes its probably that as like i said, if i select sleep it works and it goes to sleep if i leave it inactive. Won't bother fixing it as everything else works great and wouldnt wanna risk damaging something else.