You didn't mention if you started SME with acpi=off, if you haven't already,
HP Netserver & Compaq Proliant servers in most cases, won't even load Linux/SME with acpi on.
Know that HP & Compaq has a long history of proprietary hardware monitoring systems that aren't supported.
Hit enter at the SME startup splash screen and edit your selected kernel to include acpi=off.
1. Highlight the kernel you want to boot and press the ‘e’ key.
2. Highlight the line that says “root” and press the ‘e’ key.
3. At the end of the line, add acpi=off
4. Test the server.
Might want to also check latest bios firmware for ML350, not that I think it would help the acpi issue, doesn't hurt.
You didn't mention if you had a UPS?