The most recent firmware for the HTC Desire, V2.09.405.8, often gets stuck in a reboot loop. The phone vibrates, screen goes white with the green HTC logo, it then locks up.
I believe that this is related to data access somehow; so placing the phone in my microwave oven (i.e. a Faraday cage) while it sorts itself out results in a successful reboot.
UPDATE: The data access died altogether just now, resulting in the need for a reboot (and a further spell in the microvave).
The new update now being pushed out by HTC will hopefully fix this.
