I Don't Know Why This Happens But It Happens

i have a flash animation consisting of a couple of photos. Two of these photos disappear every once in a while! Yes, the same two photos everytime. Sometimes, it's just one, sometimes it's the other, sometimes it's both! What happens when I publish is it takes reeeeeeeeaally long (in the cases where the photos suddenly disappear). Sometimes I just open the library, delete the photo, and then import it again. But that's really a hassle. Sometimes when I click on the photo in the library and don't delete it immediately, Flash will suddenly crash.

I do not know what is wrong. The photos aren't too large, as some of the other photos that do not mysteriously disappear are even larger than those two.

This has caused me 'not enough memory' problems sometimes when publishing.