OK, I have finally found the reason for the alpha problem.
Normally, Xcode preprocesses your PNG files: it multiplies the alpha value into the RGB values. That's what Sparrow expects.
However, it turns out that when you load textures from a "folder reference" (as you do), Xcode does not do that! Thus, you can either
a) import them without folder reference (organized in groups in Xcode, the yellow folder icon) or
b) load them like this:
SPTexture *texture = [[SPTexture alloc] initWithContentsOfFile:@"test/shop.png"
(Note the last parameter, premultipliedAlpha.) I don't know why the old Sparrow was not so picky. Probably a difference in OpenGL ES; that would also explain why it works in the simulator.
I'll evaluate if I can do something against that, so that it works automatically. Perhaps I should check if you load your texture from a path or the root.