[Below applies only for device model NXS Rev1 with MAC address beginning with 78:A7:14:54: ]
If you are experiecing booting issues - only PWR is lit, and SIM1 (2) blinking, it seems that your device has got some file system error.
You can confirm that by connecting HDMI cable to monitor and see what is happening in the console.
This is caused by a bug in system app called 'dosfsck'. You can fix that by:
1. Put root password'
2. Execute following commands
umount /dev/mmcblk0p1
dosfsck -r /dev/mmcblk0p1
mount /dev/mmcblk0p1 /boot
3. Reboot