If from time to time your Google Talk buddies are ignoring you, that maybe because they are logged in on their Android phones and are not seeing your messages, while in the call or watching videos.
When you are on the Gmail page in your computer’s browser, you can see if you are chatting with somebody who is currently using Android by turning on the Green Robot feature in Gmail: Settings > Green Robot! > Enable. Once enabled, contacts using Android will be displayed with an Android robot icon:
Similarly, in the Android Google Talk client, contacts using Android are always displayed with the robot icon in the background.