Is the TPT bootloader unlocked? That would be great!
Tegra platforms can opt to use an AES key to encrypt the bootloader (SBK or secure boot key) so if you don't have the key, you can't use Nvflash. I thought that was the case with the TPT. Other Tegra2 devices like the Toshiba AT100 or Asus Transformer don't have a SBK so you can easily flash them.