[labens]

I found these instructions worked flawlessly:

1. Format SD Card as FAT32.
2. Copy Rom image (NapaBoth.nb0) to SD card.
3. Remove Battery from phone, and unplug the power cord.
4. Reinsert battery while holding the up volume button on the side of the phone.
5. Follow on screen prompts.
6. Once the update starts, plug in your power cord. You don't want the battery to go dead while updating.
7. Wait for approximately 20 minutes for the update to complete.

For #4, make sure you are pressing the volume up button prior to inserting the battery. Also make sure your SD card is formatted FAT32, as it is not the default for anything under 4GB.

I guess one other obvious step is to put the SD card into the phone prior to step 4.