A licorish allsort

.. nah serious .. as Dean said , another thing is saving the file in the correct format , using DXTBmp will tell you the the file type to save it as and also make sure the file is reverse to the side your painting .
A good test is paint your model with a logo for example on the cargo hatch and one side only save it exactly the same format you opened the file with .. this will determine how you are to approach the paint .