No matter which mouse button I click, I cannot select or deselect any of the vertices on a curve. This seems to also apply to when I am editing vertices on a mesh and "Limit Selection to Visible" is disabled. However, the shortcut keys of "(De)Select All", "Invert Selection", and so on do work. I've tried rebooting the entire computer and still I have this problem.
Pressed every single side of the mouse.