Information from the developer

The new Google Talk app available in a separate ZIP to be flashed on top of 20110828.

It was not included in the main 20110828 package due to having a number of bugs on many devices:

Some devices experience force-closes during video chats when attempting to switch between front and rear cameras.

Users may not appear as video-capable to their contacts.

Users may not be able to send or receive video/voice chat invitations.

* More often than not, this is due to a network issue, such as a poorly operating home router, poor carrier coverage, or a carrier actively blocking video chats; AT&T in the USA is known to do this.

Muting the user's microphone during a video or voice chat may not work.

Some users experience black screens or static on one end of a video chat.

--From wiki.rootzwiki.com/Google_Apps