That looks like a hinting problem rather than a lack of subpixel rendering.
EDIT: Or rather, it's both, but if you can't fix one you might want to try the other. Personally I've always preferred strong hinting and greyscale anti-aliasing to soft subpixel rendering.
EDIT: Or rather, it's both, but if you can't fix one you might want to try the other. Personally I've always preferred strong hinting and greyscale anti-aliasing to soft subpixel rendering.