It has not been a good day for Google. First, its extremely popular email service Gmail crashed this morning. Now, there is a virus making the rounds on Gchat, the instant message function of the Gmail. It prompts you to click a link, and then tries to get you to sign into your Gmail account, thereby offering up the hacker your email username and password.
If you get a Gchat message like the one in the screenshot below, that probably means that your friend's account has already been compromised and you should let him know (not by Gchat) that he needs to reset his password and worry about any sensitive information he had in his email account.
Below is a screenshot of a gchat message that is the virus. If you get any message that looks like this, don't click on the link!