My old faithful HP N40L just died. I had a second one in the cupboard I haven't used in years, so swapped it over... and after 24 hours it died in exactly the same way (network responds, but machine won't POST).
They sure were a little diamond in the rough. The later generations were the better part of $2k.
Might just replace it with a white box. NAS are very expensive for what they are.