Windows 8.1 upgrade has a mouse bug which creates problems for the gamers. Windows is working on the fix, but the date is still not known.
If you are a big gamer, think twice before upgrading to Windows 8.1. Many users complain that the upgrade caused their mouse to misbehave, creating a lag in video games and a few other quirks.
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Microsoft acknowledged the problem and is actively working on figuring out what caused the problem and fixing it. They are getting a lot of feedback from the gaming community. It appears that, what is known as a mouse lag, is in fact more than one issue, depending on the game played and input methods. While Microsoft is working on a patch, it did not release the date when the gamers can expect it.
There are several workarounds that some gamers found helpful: for example, if you the mouse cannot reach all areas of a game, Microsoft suggests disabling DPI scaling. It can be done with the right-click of the game's icon, Properties, Compatibility tab, and then checking the box next to Disable display scaling.
Source: Hot Hardware