There's a simple-enough way to test whether it is actually the mouse button-switch, under the left mouse button, that is the problem.
Mouse (under Hardware if in Category view)
and select 'Switch Primary and Secondary Buttons'
and then try using the right-hand button instead of the left, on your web links after clicking on OK in the Mouse control sheet, to save the changed setting.
Does that seem better?
- if so, the mouse is at fault, and after three years, has a defective button.
- if not, the system is at fault in some other way, and you can undo the 'Switch Primary and Secondary Buttons' setting in the Mouse Properties control... and either way, please let me know. Thanks.