Ah, another post merely for myself so that I can fix this the next time I rebuild my laptop. I had to get a new laptop recently, which meant a clean build of Ubuntu 12.04. When I installed Pidgin and set up my Google Talk account, it kept failing. I searched a crap ton trying to find the answer and found lots of things about different port numbers and try different servers and require ssl and use old ssl and god only knows what else. I even set about building from source thinking that some of the changes I made to my ssl libraries was screwing things up. In the end, the fix was so simple, but I never would have guessed it and I found it by digging through a lot of messages submitted in a bug report.
Anyways, the answer is that your hostname must also be in your /etc/hosts file. Below is an example.
# hostname
my-laptop
# cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 my-laptop
You can see that second line is what matters. You can have other 127.0.1.1 with other names, but you must make sure that the hostname is at least one of them.
For reference, this is the thread from which I got this info: http://pidgin.im/pipermail/support/2011-September/010777.html
