Hmm, then that means it's not the image library.
You said the non power of two jpeg loaded fine. Does the corruption happen only when there is transparency in the image?
Also just to clarify if you just draw your own non power of two image in the editor does that corrupt?
How about a power of two width and a non power of two height, does that still corrupt?
Can you also provide a screenshot of corrupted 127x128 sprite. It will help me identify what's happening since I can't reproduce it.