sounds like a fun problem
seems difficult to figure out as both will need to be DHCP to give IP's for wireless i think but that will mess things up. i take it you can choose the IP ranges that it assigns by DHCP, can you make sure the ranges don't overlap and try that?
i'm not sure if one device would take control or they would contine to fight all the time. (had a job the other day where a DHCP router was being overuled by a 2003 server's DHCP but that's different i guess).
if it's winding you up and not working, go buy a $30 switch and use that instead of a 2nd router.