I just got an Airport Express, and I'm trying to make a wireless network of an existing router. It's actually working from what I can tell, but I keep getting a flashing amber light. The error it's giving me is that I need to set it to Bridge mode, which I do, but then it reverts back to DHCP and NAT. I change the setting, restart, then it's green or a few minutes and I get the error again. Any ideas why I can't get the setting to stay in Bridge mode?