Excuse me.
googeling around I notice that many have this problem (black screen all applications with the green little light on) with leopard 10.5.2 and the latest updates.
When Photo Booth opens in Rosetta, in any account on the Machine it will result in a black screen and a green light next to the iSight. Opening the information window will not tell Rosetta is used to run the application, the box "open with" does not need be "ticked". Any guest user or any other account that has selected the Rosetta mode will system wide cause the iSight to malfunction within Photo Booth (black screen, green light). Even if you have not selected Rosetta yourself, and it will not show in the application's info window. This can be caused intentional, it can be caused by third party applications when the software is not universal. (There is no in between, it is universal or it is not universal).
It is not a hardware problem, and it does not require hardware component repair or replacement. Updating third party software and or removing ß software and even the deactivation of fast user switching can solve your problem.
Most often a simple restart will do.
When in doubt:
1. Apple menu>System preferences>Accounts>make new user account
2. Allow fast user switching for user accounts
3. Switch to new user account
4. new user>applications>ctrl+click Photo Booth>info>tick the box "open with Rosetta"
Open Photo Booth
A black screen and a green light.
Switch to another user account>open Photo Booth
A black screen and a green light.
user account>applications>ctrl+click Photo Booth>info>the application does not show it opens with Rosetta.
Deselect the "open with Rosetta" box in the corresponding account:
No black screen and a green light.
Universal software should not need Rosetta.
