Microsoft and Epic have released a minor update for Gears of War on the PC which fixes an ealrier issue relating to Games for Windows Live.
The patch, which will automatically apply itself thanks to Microsoft's Xbox Live for PC wizardry, also introduces fixes for "various performance issues".
Alternatively, you can download it from Gears of War's website, where there is also advice for people who experience problems with lost settings and custom maps.
Meanwhile, chatter on the Epic forums suggests that the patch does resolve stuttering issues for a number of people suffering from them.