Power button changed still won't turn on

I have a 3G that is about 1.5 years old. For the last 6 months the power button has been becoming less responsive. It got so bad I had to push really hard on it with a tool and hold it for about 30+ seconds to get the phone to turn off. It's very annoying that I can't close the screen manually, I have to let go to sleep.

I installed a new button and battery last night and the power button is still inactive. I plugged it into the charger to turn it on and the button does not close the screen when it's open like it should either.

I'm guessing it's got a bad connection somewhere. I'd get an iPhone 4 but I am trying to hold out for a 5.

What should I try replacing next?