This has been confirmed in the Microsoft forums.
hi all ive noticed that in some games in win 8.1 there is serious mouse lag . this makes some games almost unplayable now. this is a serious issue especially since many gamers upgraded for the benefits ingames but now cant play do to the mouse lag issues.
for me its in call of duty 4 aka modern warfare 1. there are numerous articles now about this issue and with certain games .
According to the forum moderator Microsoft is working on it
The forum moderator also sugests som workaround in the link above.