Imported Pictures

I imported some pictures from Iphoto to Lightroom 4 and now I can't pull them up in Iphoto and I can't find them in Lightroom 4.  Where have the gone.  In Iphoto they show up as a thumbnail, but when I DBLB click it shows a yeild sign with and exclamation mark in th middle of it.

Thanks for any help with this.