Let’s hope you keep your computer up-to-date. You happen to own an ATI video card, and updated to Catalyst 10.12. Now most likely you have this weird mouse lag in the top right corner of the screen. Some people report it appearing in other corners as well, both while gaming and staying on Windows desktop. Read here for more information about people experiencing this.
Rollback to previous driver version, 10.11 worked for me. For some reason I could not just install 10.11 over 10.12, because it reinstalled Catalyst CC, yet kept the newer driver version. Had to uninstall, reboot, install 10.11, reboot again, and now my mouse is back to normal.
My configuration: XFX Radeon HD 5770 XXX Edition on Windows 7 Enterprise SP1 x32.
The solution did not work so well for Ubuntu users, but they found a workaround.