Later this week, right now - something like that.
We've removed the link from the NavBar since (as has been stated repeatedly) there is rarely more than one or two people in the chat at any time. The software is still there since it is partially integrated with the forum (I don't want to accidentally break the forum) but by removing the link it'll drop it out of use.
If anyone wants to share a quick message with someone, you can use the comments system at the front of langtrees.com (you need to be registered there to use it).
Or, for those feeling particularily adventurous, you may have more fun using Skype, MSN or such and having a one-on-one session with someone.