We had the same issue for a while with our son. I agree with the tired issue, that was usually the cause. We have also done the taking something away...again, TV hits the hardest it seems. That is still the one thing that gets his attention the best...he's 4 now. One note on the time outs though. We found ours were not being effective either so we moved his time out chair to the laundry room. There's nothing in there to play with or do, so it really seems to hit home that he's in trouble. His other time out place was a corner, but he was still able to hear everything and although he'd sit and cry, it just wasn't hitting home like it should. Our laundry room is right off our kitchen, but it doesn't get all the sound that the corner did, so he feels like he's missing out on something more there. I'm not talking isolation, just removing more stimulation from him. It's really made a difference, also in how much he cries while sitting there. I guess he figures since he can't hear us as well, we can't hear him either, so he doesn't waste as much effort on screaming!