This tutorial will explain how to turn off the Sticky Edges feature of Ubuntu. This feature defines the mouse behavior when switching form one monitor to another (multi-monitor mode). When sticky edges is enabled, the mouse cursor will momentarily stop when moved to the corner of your screen (thus preventing it from moving to another screen)
To disable this feature:
Click on the Settings menu > System Settings.
Go to Hardware > Display
Toggle the "Sticky Edges" key to the Off position.