As Gster said. If you create your shader using file textures, then move your file textures, you wiill have to move the path in hypershade also for each shader.

My tip would be to get your texture files into the sourceimages folder asap as this is the default place maya looks for all file/psd file textures for each project.

MEL could fix this for you but would require yor input for the from and to path changes (in the idea I would have to create one), so you may as well just dump them in their first.