Experimenting with the CyanogenMOD custom ROM on an HTC T-Mobile G1 Android phone, I frequently encounter that the camera would get a "force close" error. After the application exists, the camera app would not start again, unless you reboot.
Since this takes some time to do, and is inconvenient, I found another way to reset the camera without rebooting.
Here are the steps.
1. If you do not have the ASTRO file manager, install it. The link has the QRCode for it.
2. Start ASTRO, then click on the "Menu" button.
3. Select "Tools".
4. Select "Process manager".
5. Click on the "Processes" tab.
6. Click on the "Menu" button.
7. Select "Killall".
8. Confirm Killall.
Your camera should be working again.
Post below if this works for you, or does not work and you found something better.