I've had my iPad 2 for one week. e-mail froze up on opening, exited, and held button, slid red slider, and device has been in perpetual shut-off mode for 12 hours now (dark screen with white clock rotating clockwise). Hooking to laptop does no goo - error message accessing iPad is shown. Am clueless what to do. Normally I would remove the battery to reboot. Can anyone help with this?

Hold down the power button and the home button at the same time. After about 30 seconds it will shut off. Just happened to me tonight after updating some Cydia apps.