From time to time, the Apple iPod Touch may get stuck at a blank screen. During these occasions, the device won’t respond to tapping the screen or the Power button, but appears to be operational in some ways.
When this problem occurs, you will need to reset the iTouch by pressing and holding the Home and Power buttons simultaneously for about 10 to 15 seconds. The screen should flash, go blank again, then restart just fine.
If the steps above don’t work for you, you may want to try plugging it into the computer and perform a restore.