An issue with Games for Windows LIVE has prevented some customers from playing games that rely on Microsoft's online services for a few days now. This forum thread has collected reports about this since Friday, most mentioning either Dark Souls or Age of Empires Online, which Joystiq notes (thanks nin) may be because these are the most popular games using GFWL. A reply from Microsoft support on Friday said: "As stated we are aware of this issue and are looking into what is causing it and for a resolution." That post was updated today with some new information:

Users are still experiencing this issue, there has been some progress; the Games for Windows Marketplace should now be correctly showing the Games Activation Keys and Live Access Codes.

We are still looking into the connection issues with various games. Some users are reporting success by running the following four commands in an admininstrator command prompt (right click on the command propt and select run as administrator)
- bitsadmin /reset
- ipconfig /flushdns
- netsh int ip reset
- netsh winsock reset

then restarting their computers, starting their game up and selecting "Sign-in with another account" and re-entering their log-in information.

This is not working for everyone and we are looking into a complete resolution for all of our users.