Question : Why can I only access the Internet if I use DHCP?

This isn't the typical newbie static IP config question you may be expecting...

I am having trouble assigning a static IP for a machine. Everything works if I go DHCP. But when I try to apply a static IP, I cannot access the Internet.  I have verified all of he DNS settings, etc., and my configs (as per IPCONFIG /all) are identical. However, if I make my static IP address the same as my previously assigned DHCP address, everythig works fine - but if I delete the address from the DHCP Lease Table, I again cannot access the Internet. So it seems like my IP MUST be in the DHCP lease table...   What is going on here?

The device assigning the DHCP is a Motorola Surfboard SBG900 cable modem/router.

Answer : Why can I only access the Internet if I use DHCP?

I have experienced weird problems with routers where the default IP address for the router has been changed.  Problems seem to be exacerbated if the client pc is running Vista.  Quite often, best solution is to replace the router.