I suppose you're referring to the fact the fuselage is spread over several texture files?
It's that way with every CS repaint kit (or at least the ones I tried: C-130 X, Xload, 757)...
This just due to the fact the fuselage texture is spread over several texture files.
this has been brought up in the 757 forum too, the only workaround I know is to put them together yourself in a new (very large) PSD, and fragment them again when you're done painting.

Lars