I already read something like this here.
The solution depends on what was the reason for happending, if it was during an edit session or so.
Sometimes defective cables (power, variax) were the reasons.
Other devices really had to be exchanged.
But sometimes users could help themselfs.
First, I would try a global reset. Hold the left arrow key down during power on.
Then you can test it and if still necessary try to reflash the firmware.
If it will not be recognized from Line6 Monkey software, you can try to boot into save mode by holding down the right arrow button during power on before you start to reflash.
If this doesn't work:
Because you say the device is brand new, I would exchange the device over the dealer where you have bought it.
You can also bring it to the service center in Australia, but have to make guarantee things clear with Line6 first.:
Adresses and infos you can find over the Support link on Line6 homepage right above. Keep the mouse pointer over Support..
Music Link Australia
Servicing: Electronics, Guitars 29 South Corporate Drive
If you want to try getting it back in the game before raising a support call, it may just be a firmware glitch.
First try a Global Settings Reset - Power Up while holding down Nav Pad Left. This can can get you out of a start-reboot loop if the patch you last used is corrupted because it defaults back to Set List 1 Best of HD 1A Son of Plexi - if you use this with the POD HD500 you will need to recalibrate the expression pedal and rename Set Lists 5-8 back to whatever they were named prior to resetting the Global Parameters.
- Global Settings Reset HD500.http://line6.com/support/docs/DOC-2222
- Expression Pedal Re-Calibration HD500 http://line6.com/support/docs/DOC-2223
If that does not help then you could try Power Up and Nav Pad Down. This gives direct access to Flash Memory update mode. Now use Line 6 Monkey to flash-update your firmware to the latest version. If you do this and it works then do the global settings reset described above afterwards.
Video demonstrating use of Monkey is here --> http://line6.com/support/docs/DOC-2057
The Global settings reset will not overwrite any presets that you have created. The Flash memory update will if you choose to overwrite your presets during the update process. For you, if you have not created any meaningfull presets yet then I suggest that you choose to overwrite, just to be on the safe side.