Instead of using the Google Talk client embedded in Gmail, why not use it in your sidebar instead?
Thanks to the gTalk sidebar extension, we can do just that.
Once you roll out the extension, you’ll need to add the button to the toolbar.
Just keep in mind that if you terminate the sidebar, it will terminate the client as well.
This extension is also extremely useful for sending somebody a quick email.
Clicking this button will open up a message window already addressed to that contact.
Note that you’re free to also use the keyboard shortcut Alt+G to bring up the sidebar.
Install gTalk Sidebar from Mozilla Add-ons