I have a project using hair for grass and particle halos for fireflies, you can see where I am getting at with this. Problem is that the render engine renders the hair over the halos and is looking like this.
Uhm… I ant no expirt…Jet… but a few experiments gave me an Idea that might help you.
in the modifier tab you will see your pixels,that is if your using blender 2.5.I don’t know about the other blenders.Click convert and I believe that will make you’re hair a type of mesh.I don’t know if it will help withe the halo thing. I also think that you can turn your hair after converting them in soft body’s.Don’t ask me were to find the soft body’s I one’s just stumbled upon theme.
It looks good,looks like you placed a lot of Passion’s into it.If I may sagest.Try making the moon a bit more realistic. and make the yellow thingy in the flower more round it looks a bit triangular.
I’m facing the same problem. Did you find a way around it?
To make this more complex, I’m using Blender 2.49b.
I will update here if I find anything.
Try rendering the halos out on a separate render layer then use the compositor to add them to the original render.
try this tutorial to see how you can set up a particle system which emits light and also glows like the halo effect…would probably help with your scene…just add the particles to a new render layer once done.
http://live.interwebsitedesign.co.uk/index.php/home
i know its not answering your question, but halos are not used that much anymore 
