Photo Booth won't open!

Hello

So my Photo Booth worked very well until now.

But today when I tried to open it, the icon appears in the dock but it doens't open and then the icon disappaers again from the dock.

I read here on the site that photo booth won't open if any other application is using the cam.
But there isn't any other application where I use the cam. (I don't use iChat)

But then today I used the cam do to a picture on facebook.com. They use Flash Player to do the pic and you have to accept that they can use the cam. I already tried to no accept that, or to disactivate the flash player plug in from firefox but Photo Booth still won't work.

In the Photo Booth terminal they write that:

Last login: Sat Feb 7 17:26:06 on console
/Applications/Photo\ Booth.app/Contents/MacOS/Photo\ Booth ; exit;
macbook-de-anen-taina:~ anentaina$ /Applications/Photo\ Booth.app/Contents/MacOS/Photo\ Booth ; exit;
2009-02-07 17:42:01.112 Photo Booth[161:10b] Unable to load nib file: MainMenu, exiting
logout

[Opération terminée]

and I don't what I have to do...

already though to get rid of firefox and install it again, but I wanted to know if there's any other solution before I do that.