labels with backgrounds

I have been trying to publish my layer and keep getting "Layer is using unsupported setting (KML)". Is there a way in the flex viewer to change the label background. I simply want a label that has a solid background so that it stands out. Does anyone have a way to either publish the service with the label style I want or change it in flex?

As well, is there a code I can put in the text to add a carriage return, that is a bonus.

Thanks,
Mike