Troubleshooting jumpy mouse cursors in OS X
Periodically, some Mac systems may experience jumpy cursors when using mice. Here are some options for troubleshooting this behavior.
The operation of the mouse and pointing system in graphic operating systems is one of the more important aspects to having a smooth experience when using your computer. Even though Apple and other computer manufacturers are incorporating more multitouch options for interacting with computers, the mouse and pointer is still one of the primary options for managing the system. If something is wrong with the mouse pointer and you get jumpy or erratic behavior, then this can really impede on your ability to use your system. Generally if this happens you can quickly fix it by running through some basic troubleshooting steps.
The first thing to do whenever you experience tracking problems, either with the cursor jumping or pausing, is to clean the mouse. While cleaning used to be a primary concern for mechanical ball mice, optical mice can still be affected by dirt. Recently a significant amount of skipping behavior in one of my optical mice was fixed by removing a large wad of lint that had been lodged in the optical sensor's hole. Using a clean and lint-free cloth or Q-Tip, wipe the sensor lens.
The second thing to do when troubleshooting a mouse skipping is to check the tracking surface. While optical mice have advanced to be able to track on most surfaces, some still have troubles, especially with soft, transparent, or uneven surfaces. Try using the mouse on a flat, opaque, and slightly textured surface (a plastic cutting board usually works great) to see if the tracking improves, and if so then try using a new tracking surface.
You may also want to check how the mouse is connected to the computer. If the mouse is wired, check the cable by moving it around to different positions to see if the skipping behaviors stop (this may be especially true if the mouse only skips when in certain positions).
If your mouse is wireless, if your Bluetooth or Wi-Fi interfaces for the mouse are not working properly, then the mouse could start skipping. Usually this happens if reception is lost either because of interference, faults in the mouse's transmitter, or faults in the computer's receiver.
To test for reception, try physically moving the mouse closer to the computer to see if you can pick up better reception. In addition, try checking for any nearby electronics and move them or move the computer away from them to see if that helps. Bluetooth and other Wi-Fi devices use the 2.4GHz radio frequency, which is popular among numerous devices and therefore may contain a lot of noise and interference.
Another aspect to consider for wireless devices is batteries. If the battery on your mouse is running out then you can not only have shorter reception range but the device may regularly go into sleep mode or even shut off altogether. If this happens, the mouse may pause on the screen, so try replacing the batteries or charging your mouse if you have one with a recharging dock.
For any mouse system, use only one input device. The pointer in OS X will sum the input it gets from any pointing device, so if you are using one device and inadvertently touch another device, then the cursor may migrate around the screen in unexpected ways. One area where this has happened is when people have several Bluetooth travel mice that they have left on. In some cases if a mouse is in a drawer and the sensor is barely picking up a surface underneath it, if your computer is in range of the mouse it will pick up the mouse's attempts to track and move the cursor accordingly. Another more common dual-pointer setup is for systems that have both Apple's magic trackpad and a mouse (laptops as well as desktops that have the Bluetooth version of the trackpad).
To overcome problems with dual inputs, you will have to locate and remove them from the system. Check your Bluetooth settings to see if you have any actively paired pointing devices, and also check to see if any are physically plugged into the system. You can do this with the System Preferences, or you can check both the USB and Bluetooth sections in Apple's "System Profiler" utility to see what devices are attached to your system.
The last way to test for mouse problems is to get a new one. If you have tried everything to stop odd behavior with your current devices and you cannot get it to stop, try using another mouse. Borrow one from a friend to see if the problems persist, and if not then just replacing your old mouse may be an easier and hassle-free option.