This can almost always be traced to the physical connection, i.e., the "plug".
The good news is, if it's the plug on the end of the mouse cord, replacement mice are pretty cheap. It might even be worth going to an optical, or (dream-on!) a cordless/optical.
The bad news is it might be the connector in the laptop, which is typically built on to the motherboard. If you're still under warranty or have a maintenance contract, have this looked into, NOW. Out of warranty repairs for laptops areridiculously expensive.
Prevention? When the mouse is jacked in, make sure nobody does anything to stress that connection (the possibilities are endless). When you are unplugging, and especially plugging back in, do so as carefully as possible: make sure everything is lined up right, don't do it by feel.
Consider getting a dock or at least a port replicator. The connectors for these are built for the old in-out-in-out. Failing that, if your laptop can handle USB, then consider a USB mouse, again largely because the connection points are built to handle the rough stuff. (Your typical serial port was really designed and built with the needs of a desktop in mind: set it and forget it.)
One other advantage of a USB mouse (or keyboard for that matter) is that is your device does freeze, you can usually unplug it, jack it back in or even replace it, with the box running.
