(new) Apple I-macs Webcam Problem

Hi all,
yes I've searched and looked through the threads;
new I-Mac;

the built in web cam works fine elsewhere..
When in the chatrooom, ive clicked the (my) cam 'camera' icon on the left
(and it then has a green outer ring arond the icon)

its then 'lists' my webcam as being one of the Live web cams..

but no pic for me (in my own left cam window)
and nobody else can see a pic either?

any ideas anyone ??? its so frustrating?
Many thanks...

BINGO !!

found a link below for "mac book settings"
wasn't that clear at first... but to do with setting it to USB (even though its built in)
(strange)

but its just worked .. Very Helpful, and Thank you.

Hurrahh!!!