Help me open iPhoto!!! :-/

I try to open iPhoto and I get this error message:

Your photo library is either in use by another application or has become unreadable.

Shut down and restart your computer, and then open iPhoto again. If the problem persists, try rebuilding your photo library. To do this, quit iPhoto, and then reopen it while keeping the Option and Command keys pressed. You can also try restoring your photo library from a backup.

I've done everything requested in error message, but it still will not open and the same message keeps appearing.

Can someone assist? Thanks