One possibility is to check out what the router can do for you. I need static IP, too, and I found a way to get the router to assign static addresses based on the MAC address of the network card. Assuming your router has it, then you could use it to resolve the conflict and let the Network Manager get an "auto" address that will satisfy it (even for multiple cards on one system, or ethernet vs. wireless, for instance.) It's under Lan IP Setup - Address Reservation on my Netgear router, but it could be called something different, and hidden elsewhere in the menus on another router.

Cheers!
Krishna