Laptop curser “jumping” and Server 03 network

I am having a problem with multiple laptops connected to a Windows
Server 03 active directory. The laptops’ cursers jump around when the
users are typing in Word or Outlook. All of these machines run XP pro.
Some were converted from XP home to Pro and some came with Pro. All
machines have been reformatted with a clean copy of XP pro. The
original drivers for the keyboard have been downloaded and installed.
The machines are Gateway, Compaq, HP, Dell, and Toshiba. The
problem started 3 months ago with these various machines when we
networked our office. The only thing they have in common is the
network. Can anyone give relief to me from the end users????