for placed vector art - use the *place...* command, turn off anti-aliasing in the properties bar, size the image to fit your skin, then hit return.
Also for a GUI i presume you will have to make the image Indexed colourr - *image>mode>indexed color*.
This will limit the colours used from now on to the colours already in the image (so if there are 50 colours in your image you won't be able to use a colour that is not one of these.
Once in indexed colour mode, anti-aliasing will be OFF.
Turn off the anti-aliasing in the text tool - text tool property bar *aa > none*, (off in Indexed colour mode.
Hope this helps, if you are still stuck, reply to this with a 'detailed' description of your problem.
Moe: It could have been a real ugly situation, but luckily I managed to shoot him in the spine.