check if the texture files are in the sourceimages, we had our texture files in a folder, inside the souceimages folder during the group project and something like this happened, then maybe set project and try reopening.
Kinbi, you star. I did exactly the same thing- I had a folder of textures within source images. moving the textures into ounce images and deleting that folder worked a treat.Thanks for the heads up! All fixed now! :D