Wireless Problem with Time Capsule - Connected but no internet

I am having problems setting up a wireless network using my Time Capsule.

I have just moved from one building to another in the same complex - it worked just fine before, but in the new apartment I can't make it work. The ISP here does not use DSL - it's an ethernet connection into the wall - theoretically each computer should connect directly via an ethernet cable, but I need a wireless network. So the TC is connected via an ethernet port to the internet, and if I plug an ethernet cable into the TC and connect to my MBP I have internet connectivity. So the TC works perfectly as a wired router. But when i create a wireless network - whether I use bridge mode or NAT - I can connect to the wireless network, but not to internet. In bridge mode I get a self assigned IP address, and using NAT I get assigned an IP address but no internet connectivity. Via ethernet through the TC I am properly assigned an IP address from the ISP's router.

Does anyone have any suggestions??