Creo Illustrate bad url issue

Hi again,

Yet another issue with Creo Illustrate 7.0 -  See the image below - 2nd warning. I don't care about first one at the moment.

Sometimes when I open c3di file some of the images that I inserted as symbols (png format) go corrupt with this error message. I think it's once again something to do with saving, but how can I make sure I don't need to recreate it later on risking with every save that something goes to hell?