I held down my enter key for a long time until all of the messages went away. Then when I tried to save the fla with a new name, it told me that all of my images in the fla were corrupt and that I should delete them.
I was able to pull the changes I had made to some navigation into an older version of my fla and replace the older symbols. However, I'm guessing that had I deleted the corrupt images, then re-imported them, I would have been ok, as my timeline and symbols on the corrupt fla were intact.