Hi and welcome!
Couple of starter questions. What program are you editing with? And secondly, what format is the texture in?
Sounds kind of like what happens when a compressed texture format like DXT is opened in an editor. You can use DXTBmp if this is the case. Take a look at this tutorial for how this works.
http://www.simmerspaintshop.com/foru...ng-fs2004.html
And feel free to post back if you get stuck, we'll try to get things going.