thanks for the compliment, much appreciated, coming days we will release a version with raid support.
To check if u-boot is loading you have two options:
(1) make a wired connection to the serial port on the mainboard, you will need a usb/serial 232 cable TTL lvele 3,3 V.
(2) use clunc and netcat to talk to u-boot via the network card. However this option may not work in case u-boot is halted or hanging to early.
Regarding option 2.
In fact this option is making use of the "net console" that is compiled in u-boot as present on the lacie nas devices. This net console can redirect output/input that is normally sent/received via the serial port to the network interface instead.
How it works ? u-boot checks for a few seconds if it receives a "lump" signal on its network card (in fact a magic packet) and if it receives one it switches to net console mode and redirect in-/output to the network interface. It hen goes in command line mode waiting for further commands to be received via the network card. If no lump signal is received u-boot continuous its normal operation and tries to load the firmware from disk.
I also tried clunc as Mijzelf described using (computer and nas directly wired to the router):
./clunc -i 192.168.1.155
And nothing happens.
What clunc does is sending this lump signal and tells u-boot which ip address to set. After clunc has interrupted u-boot you need a program like netcat to make a connection to your nas to talk to u-boot. So clunc alone is not enough. The fvdw-sl console that runs under window can do this for you, sending the lump signal and open a u-boot console window. (see plugout net)
There is one point if u-boot fails to load or hangs before it is able to check for the lump signal and load the net console, then of course you won't be able to connect via the network interface. Then the only way is use a wired connection to the serial port. The fact that you see some live on the network connector gives some hope.
As said the fvdw-sl console could be of use to you to check if u-boot want to talk to you via the network card. If u-boot hangs to early then you need a wired connection to the serial port.
Again to modify u-boot in flash you need either to do that in u-boot itself by uploading an image and write it to flash or use from linux userland a driver to overwrite the flash. This last option is not available in the standard kernels AFAIK. So I don't think it is an u-boot issue, hopefully it is not another failure of the mainboard