Well that isn't good. We've had no other V3 problems and the boxes we've tested here work as expected.
Do you have anything plugged into the USB sockets? If so try removing them and booting again.
Try powering on the box using the switch on the back whilst pushing a pin / biro or similar into the reset button below the LAN port on the back. Does it now boot?
Finally, try a different HDMI cable and TV. Just as a test.
The problem sounds like either a power problem (not enough power to boot - that's why I recommend removing external devices) or a HDMI handshake problem (device isn't able to correctly communicate with your TV to establish correct resolution and this causes it to stick on boot).