I've been trying to work out why I get this error...

https://onedrive.live.com/?cid=b60c11d037429d8e#cid=B60C11D037429D8E&id=B60C11D037429D8E%2130669&v=3

...for a long time. I have checked in image editing software, Corel, which says that the texture is 256pixels x 256pixels. I also have a higher res. texture of the same but 512pixels x 512pixels. Using the lower res, for LOD and the higer for close-up. No matter which texture I use I get the same error.

This is really bugging me, I can't find a solution. Help!