Some users have experienced a longstanding issue in which the cursor freezes on the screen, seemingly at random intervals. The problem generally forces a system restart.
Apple Discussions poster arthurms writes:
"Quite often my mouse cursor freezes up on the screen and my only remedy seems to be to shut down and reboot."
This problem has persisted since Mac OS X 10.5.2 for some users, and while recent updates have reduced the prevalence of this problem, it still occurs. It seems this issue is not necessarily systemwide; it occurs in certain applications, such as older Firefox version, and the login window more than others. As such, the relevant fixes for this problem can be hard to pinpoint, but the following may help affected users.
Fixes and Workarounds
Unplug and replug the mouse Unplugging all peripheral devices including the mouse and then plugging the mouse back in (trying different USB ports if necessary), may help restore the mouse functionality; however, if not then users will have to restart. While users have resorted to restarting the computer by holding the power button down, this is not a recommended way to restart, since it has the potential to harm the system. Instead, users can bring up the shutdown menu by pressing "ctrl-eject" on their keyboards. When the shutdown options display, users can press spacebar to restart or enter to shut down. Alternately, users can send the shutdown command to the computer via the Terminal. To do this, press command-spacebar to open Spotlight, and then enter "Terminal" to search for the terminal application. Upon opening this application users should enter "shutdown -r now" to immediately reboot the system. While this command does not allow the whole system to properly shut down and as such should be used sparingly and only when necessary, it is still better than holding the power key.
Update driver software For users with third-party mice, updating the driver software may help the situation. If there are no updates from the manufacturer, users can try other driver software such as USBOverdrive (http://www.usboverdrive.com/).
Update affected applications Some users had this problem with version 2 of the Firefox browser, and upon updating to version 3 found that the problem's frequency was greatly reduced. As such, if any application has this problem, we recommended that users update the application, or reinstall the it if there are no updates available.
Reset the PRAM The PRAM on the computer stores some mouse-related parameters that load before the user-specific settings are loaded. If there are conflicts or faults in these settings, it is possible this could lead to problematic mouse behavior. To reset the PRAM, reboot the computer and hold the options-command-P-R keys all at once. The computer will reset and make the boot chimes continually as long as these keys are held. After a few resets, release the keys and allow the computer to boot normally. The mouse settings should be set to their defaults, along with some other system settings such as audio volume.
Reduce mouse tracking speed Some users have found this problem seems to be lessened if the tracking speeds in the computer are reduced. While this indicates problems with the mouse driver, it could be a matter of problematic hardware as well that leads to the freezes when sampled at certain rates by the computer. In the "Keyboard and Mouse" system preferences, reduce the mouse speed a little and see if it helps the situation.