There is a great little instant messaging utility, Pidgin that helps to find who has blocked you in Google Talk
It’s very simple. Just follow the steps:-
1- Log in to your Gmail account on Pidgin.
2- Go to “Buddies” -> “Show Offline Buddies“. (A person who has blocked you must be showing offline to you. So you need to make all offline friends visible)
3- Now all your contacts are visible to you. Pick any one of those.
4- Right Click on your chosen contact name and select “Get Info“.
It will show you the brief information of your contact. Now, if any of your contact has blocked you on Google Talk, you will not be able to see his/her profile.
6- Select a contact who you think may have blocked you. Again, Right Click on his/her name and select “Get Info“. You will not see anything. Not even the contact’s name.
This goes to show that this particular contact has blocked you on Google Talk and don’t want to talk to you and so it appears to be offline always.