Hum, that's strange my Dell R200 stops at the same day March 14 with exact the same symptoms. It turns on, but after a while it stops with the system indicator on orange/amber.
I have the server here on my desk but I have no clue and also no spare parts to test if it's the cpu/the motherboard or the power supply.
I have tried removing memory sticks also with no luck. Still the same.
Did you already found your faulting part? Or still no luck?