Noverina,
Here is a fix for the "Could Not Start The Camera" message, which worked for the BB Pearl 8100. It is claimed that it should work for other models as well. Supposedly the source of the problem is the browser cache that needed to be cleared.
1. Go to your Browser app
2. Select the App button
3. Scroll way down and select "Options"
4. Select Cache Operations
5. Clear everything (history, content, cookies etc)
6. Select the return key (shows clearing memory)
Here is a link to the Crackberry forum regarding the same issue:
Camera Error - BlackBerry Forums at CrackBerry.com
Hope this helps. IMO - you have faulty phone that probably needs to be replaced.