The vast majority of issues with the tablet (such as a freezing or unresponsive screen) can be resolved by fully shutting down, and then re-starting the tablet.
A single touch to the power button puts the LeapFrog Epic tablet into sleep mode, it does not fully power the device down.
To fully power cycle the tablet:
1. Press and hold the Power button for 2 to 3 seconds
2. Choose "Power off"
3. Confirm by selecting "OK"
4. After the device has powered off, hold the power button for 3-5 seconds to power it back on