Hi Mike, I have the exact same problem on my server. I simply upgraded from 4.1.1-P1-15+squeeze8 to 4.1.1-P1-15+squeeze9. Given the patch you attached, this is very strange. But after downgrading back to 4.1.1-P1-15+squeeze8, everything was fine again. So there seems to be indeed a (critical) issue with 4.1.1-P1-15+squeeze9, as it basically breaks the DHCP server.
Cheers, Olivier
