If your cursor is barely working on the vertical axis the first thing to check is that the switch on the base of your mouse is set to ON and not PRESENT. As when your mouse is in presentation mode you can only move your cursor vertically by picking it up of your desk and pointing it up or down. 

If you are a Mac user one other possible cause for behavior like this is if you still have the Swiftpoint Manager installed an enabled on your system.

The Swiftpoint Manager software is only for the Swiftpoint GT, newer Pen-Grip models use the Swiftpoint Control Panel. You can tell the difference between the two at a glance by the color of their icon. The GT's Swiftpoint Manager has a Blue icon, while the Swiftpoint Control Panels icon is Red.

So if you have the Swiftpoint Manager installed but do not have a Swiftpoint GT, or do not plan to use one on this Mac you should uninstall it. Alternately if you do have a GT and will sometimes use it on this system, you can just temporarily disable the Manager using the button highlighted in the screenshot below.