Mouse Stops Working & Freezes

My daughter's Macbook Pro (almost three years old) can go for months and not have this happen. But today once again the mouse stopped working, froze, and could not be made to move. She did use the up/down button for a while to read a page but otherwise the notebook was unusable. She turned it off for about an hour, but when she turned it on the internet connection kept cycling on and off. When I unplugged the Linksys router and replugged it in, the connection was better but then the mouse problem showed up again! Can anyone help with the mouse problem first of all? Is there some type of "tweaking" that could be done? Or is this a sign the notebook is getting too old? Thanks!
P.S. I have no idea what is causing the intermittent network drops but that's another thing.