I've just had a quick look at the file you've suggested and you're right.
I think I know what the problem probably is:
The file is 1024 x 256
A standard pc DDS file stores the dimensions as height x width (256 x 1024)
DXT files store the dimensions as width x height.
My converter reads dds files as width x height. This doesnt matter when dealing with square images, but of course, when there's a non-square image it breaks. This is why the bug's not been noticed before.
I'll upload a fix now.