Are you feeling very-very annoying with "Media scanner running..." message? Unable to run your camera apps in android. Some might suggest you to Factory Reset your phone. Wait! Try this it might help.
It help me and hope it's help you as well.
What you need to do is Run Gallery and open all pictures inside... browse thru the pictures
DO NOT close the Gallery. Run your Camera again..... You should not have the annoying message again.. Good Luck and Smile :)
Worse case. Backup you photo then.... Setting > applications -> all -> media storage -> clear data
Another solution you could try
First, remove memory card from phone and copy all memory card data to pc, then insert again to phone, and format the memory card.
Finally, copy all data from pc to memory card again and insert card to phone. reboot your phone.
This problem might happen when you try to change Camera.apk inside System/App...the system going crazy :)