iphoto cant find photo

Hi there....

Running Mountain lion on a week old 27inch imac.

Started to photostream some picture that migrated over from my old mac, first few albums I streamed to people work great.

However, now when I go to select some pics from a trip to the US back in 2010 when i select the pics i want, and then hit share it comes up with: -

The photo “IMG_xxxxxx” could not be opened, because the original item cannot be found.

But I'm not trying to upload any photos that it names.

Someone please help as this mac is going out the window and I'll stick to my 7yr old imac on Snow Lepoard that never casued me any hassle.....it just worked!