Why are all contacts grayed out in Google Talk?
I did some tests, and turns out that the contacts are grayed when your phone's APP isn't able to communicate with Google Talk servers.

This is also the behavior when using Google talk on other systems, or even from Google web pages, like Google+.

You didn't noticed this before, most likely because you never had a communication issue with their server, witch is good. I have my grayed contacts all the time :(