Galaxy Tab 2 10.1. After an unknown update awhile back (my wife's tablet, but she thinks it was a system update), the tab appeared dead. Cracking the case let me verify the battery had a full charge. Connecting it to a PC showed me it seems to be trying to boot (OMAP 4430 driver request) but fails and reboots. This loop has a period of about 2 seconds or so, making me suspect the bootloader or boot chain is corrupt.

Screen never comes on, so no logo or icons are ever seen.
I have yet to make it shut down except for running the battery dead.
vUP+Pwr, once finally off, starts the loop again once I let go.
vDwn+Pwr does the same.