If you have a wireless mouse, low batteries
can result in weak, mixed or no signals that can affect its functionality so start by replacing them. If you are using a ball mouse, remove it and clean the rollers as dirt and gunk will cause erratic
behavior. If its an opitcal mouse, "jumpiness
" and "jerky
" movements can result if using it on a glossy surface or reflective mouse pad. In some cases using multiple or uneven mouse pads can produce the same results. As a test, try placing it on a piece of newspaper or rubberized pad to see if that resolves the problem.
If that does not help, confirm that the mouse works on another machine. It is possible the mouse could be defective or has gone bad. Another thing to try is to use a different mouse or a PS2 adapter
if its a USB mouse.
If this is an issue on a notebook or laptop, please see Disable Touch Pad of your Laptop; Avoid Erratic Cursor Movement When Typing