When using iPhone 2.0 applications, I've seen the iPhone Black Screen of Death (not to be confused with the M$ Blue Screen of Death) several times. It occurs when accessing some iPhone Applications. When it occurs, here are the steps I used to reset my iPhone.It would be nice to see a KB article on the Apple or A$ site!
1. Turn iPhone off and on -- Press and hold the Sleep/Wake button for a few seconds until the red slider appears and then slide the slider. Then press and hold the Sleep/Wake button unti the Apple logo appears.
2. Press and hold the [Home] button for at least six seconds, until the application you are using quits. (This worked several times for me.)
3. Reset the Phone - Press and hold the Sleep/Wake button and the Home button until the Apple log appears. (This worked for me serveral times).
4. Reattach the phone to iTunes. (This always worked but my laptop was always with me.)