Users attempting to login were stuck in a continuous looping cycle leaving them with the uncertainty that it might be due to their Windows machine. Rebooting of course didn't work; so some people here thought it was a problem with their station and tried to re-install Google Talk only to discover that it is no longer available. I too learned this lesson the hard way after having to re-installing Windows due to an audio problem (which incidentally was triggered by Google Hangouts).
It seems to be an all out withdrawal from supporting the Windows platform; similarly Google Sync which allowed Outlook users to synchronize Google calendar was formerly ended last July. It's well known that within the Googleplexes of the world, that Mac & Linux usage far outweighs Windows; in fact a contact of mine said that you'd practically need CTO approval to get Windows. Over/under bets are currently being made as to which year Chrome support will be dropped from Windows ;)?
It's tough to start the week off with this outage, and while I'm happy to see it running again, the concern however that support for this product may permanently go away since Google declared that the Talk would be deprecated (done away with), in favor of Google Hangouts. Our office relies upon it significantly and will need to find a replacement if Google Talk support completely stops. Google Hangouts is just plain clunky: prone to having video complications, poor quality & delayed audio and the text chat feature is not well integrated. The simplicity and quality of Google Talk is usually spot on; both within the desktop app, gmail integrated pane and the Android app.
For now, I'll be holding my breath to see if another viable replacement comes along for Google Apps based communication.