~200kb Plasmid DNA purification is not working - (Jul/06/2011 )

I have been trying to do plasmid DNA purification for FISH for the pas three months.
I've used the PrepEase kit by USB. After running digestion, the bends look better with the kit.
However, they are not pure at all. I keep getting a bend that looks like a chromosomal DNA on the top of the gel.
I get several smaller bends with faint smear, as well.
I've tried doing ultracentrifugation, but it ended up giving me no detectable bends.
A couple of other protocols didn't work, either.
What can I do? any protocols that worked for you?

Hola, Quiagen has a large constructs kit (Cat 12462)that I have used for bacmids purification of more than 100kb and it´s fine for me, but the starting culture volumes have to be high. Buena suerte