Network icon in FInder gone

I am trying to file share between my ibook and my imac. (which has worked many times before) I am able to get to my imac from my ibook but I can't get to my ibook from my imac. The network icon in my finder window on my imac is gone. I can't seem to figure out where it went or how to get it back and I have no idea how to get to my ibook without it.

Message was edited by: lostkat