Nearly every Google Nexus One user has a Power/Lock Button problem.
Here’s a fix for this.
Go to the Android Market, and install the following Apps:
- Lock Screen Widget by droid-mania.com
- Quick Boot (Reboot) by Sirius Applications Ltd.
Warning! Quick Boot requires Root Access.
Both Apps are free of charge.
To add them, make sure you have at least 1 Home Screen with free space.
Tap and hold on the empty space, go to Widgets, and select “Lock Screen Widget”.
Next, tap and hold again, go to Shortcuts, and select all shortcuts that share the logo of Quick Boot.
It’ll look like this:
Posted in 
Hi I had the same problem with my power button, I came a cross an app called “fix power button” it’s free and works great. press the volume control to wake screen, press back and your screen appears. I wasted a lot of time trying to find an app that works, this one does all you need to do is install an app to lock the phone and it’ll go into sleep mode, press the volume and the phone screen appears.
I LOV THIS APP THANK YOU