The problems started about last year when we noticed that the DHCP server in our Windows SBS 2003 server kept stopping and refused to restart itself. It would only restart if it was done manually through the services control panel. Puzzled, we finally invested in an external consultant to monitor the server throughout the day to see what was causing it. It turned out to be an iPhone connected to the network, which was trying to act like a DHCP server causing a conflict when the SBS DHCP server was trying to assign IP's. Digging down further, it was identified that the particular iPhone that was causing the problem happened to be a jailbroken phone which had PdaNet installed (version 1.61). It turns out that every time this app is turned on to the WiFi Router Mode, it broadcasts itself out to the network and creates DHCP conflicts. By putting the app in 'Off' mode within PdaNet settings, the DHCP issues went away immediately. I wanted to make sure this was documented just in case other folks are having similar issues.