DHCP Server not functioning - disable RPC filter in ISA

I found a weird situation on one of my SBS servers where DHCP wasn't working. When I went into the DHCP management console, I saw this:





After some investigation, I had to disable this RPC filter in the ISA firewall. Of the 9 SBS boxes I manage that all serve DHCP, this is the only box I've ever had to do this with. So weird. Here is the RPC filter in application filters I had to disable: