I have a customer who informs me that you MUST use dynamic IP addressing (DHCP) the first time that you connect the camera to the router wirelessly. Once initially connected via DHCP, then you will be able to manually change the IP addresses.
I am not sure if this is specific to the Lynksys Wireless G Router or whether it applies to other routers as well. I would be interested in hearing your feedback. Please leave a comment or drop your response off to firstname.lastname@example.org.