I got a solution for that issue. It works for me. I think the reason for not showing maps is proxy settings for the emulator is not set properly. By inserting proxy in settings.db, we set the proxy for the browser only. it neither set the proxy for map nor GTalk.
In windows there is a software, Proxifier which can be used to direct all the network request to a user specified proxy. It direct all the requests to the specified proxy. Here we don't want to set any proxy settings in the emulator.
http://www.proxifier.com/.
But for ubuntu i didn't get a solution yet. Hope you would try having Squid proxy server running in your own machine
configured to direct all the requests going out from your machine to the parent proxy i.e. your real proxy.
regards,
wageesha