No previews icons on my external hard drive for EPS files

I'm not getting all the preview icons for most of the EPS files on my external hard drives. It shows all JPGs, TIFFs, PSDs etc.. It seems to create the preview images for the EPSs last and than shortly after displaying them they start popping up as generic "EPS" icons. But if I keep scrolling down it keeps creating preview images of all the other file but will onlt show generic icons for the EPSs.