I also thought so.

I had two working N900. I flashed them couple of times (also nolo-part). Always with the same cable and with the same computer. Then I (intentionally) flashed modified xloader (signed part). N900 instantly went black. After shutdown with battery removal it feels bricked. It can't be powered on. It will not show any more in kernel logs. I use working N900 for reference (cold flashing, kernel logs) and to charge batteries.