Hi there, my name is Aaron, and I'm a Games for Windows Live developer at Microsoft. We have been tracking some of the crashing problems reported with G4W-L on these forums, and I wanted to give a quick update. Specifically, the issue I'm describing is:
After starting Gears of War, play proceeds for about 20-30 seconds before game crashes.
There are presently two known causes of this problem.
First, running from the DVD Autorun menu triggers this. The workaround is simply to run the game either from the Games Explorer (Start Menu->Games) or directly from the game folder in Program Files instead. We know where this is occurring, but are continuing to investigate why it is happening.
Second, some anti-malware programs have incompatibilities with G4W-L. For example, we have seen problems with older versions of Spyware Doctor, Karpensky and ZoneAlarm. Upgrading to the latest versions of this software generally solves these problems. We have found that merely turning off the software doesn't always help (and we would not advise de-activating your anti-malware anyhow), since the software is generally still doing something in the background.
If you are still having trouble beyond these two causes, or have found an incompatibility with anti-malware software I haven't mentioned here, please feel free to reply to this thread or message me directly. In the latter case, we have been working with these companies to make sure that the G4W-L problem is properly solved.