A Land Far Away

I appear to have a corruption with textures in my area. a cobblestone texture which is painted down is not showing up when mousing over it, the space on the available textures for the tile is white instead. Program is crashing out when I try to use the swapper too.

Does anyone know a fix for this? Can I swap out the file containing the textures from an earlier version? any one know which file in a directory that is?