N5200 stuck in boot :(

[wintergreen]

Hi all,
I've got an N5200 with 3x1TB raid 5 but when I power it on, it won't complete startup.
It gets as far as assemble raid, where it takes ages, and then goes to self-testing, where it hangs. If i press the power button, it says it's shutting down but never does (I have to pull the plug)
The strangest part is that it makes no difference if i disconnect all the disk drives.
What can I do?
I have tried holding down the reset button for 10 seconds but this doesn't do anything, and i can't access it via the web interface (firefox reports the connection is refused)

[wintergreen]

panic over... it turns out it is all working ok, it's just taking a very long time to complete the checks for some reason...