Are both networks configured using DHCP?

The automatic location thing only works when you have DHCP at both sites, so that your machine gets its IP address, gateway, etc. automatically when it joins the network.

If you have your home network configured statically, for example, to use 192.168.1.x addresses, but the office uses something different (e.g. 192.168.0.x), your Mac won't know this, and won't be able to communicate with others.

I use DHCP at both work and home and my AirPort has always (even prior to 10.2) automatically configured itself appropriately.