I was having this same problem. All of a sudden the pointer of my new USB mouse froze in the centre of the screen. It would not move, though i could click both the buttons and scroll too. After a lot of surfing the internet, and a lot of brainstorming i came up with this idea. I don't know if it will work for PS2 mouse. Anyways, here are the two things i did:

1. Go to Start menu. Type services.msc. Find Human Interface Device Access. If it is set to stopped, start the service. Double click it, and from the dialogue box select Startup Type Automatic. Press OK.

2. Restart the computer, and enter the BIOS Setup Menu. Go to Integrated Peripherals. Select USB Mouse and set it to Enabled.

These steps has completely solved my freezing pointer problem. Hope it helps the others too! :)

NOTE: If its the USB keyboard that is causing the problem, then you can check its status here in the BIOS setup, just in case it is disabled here.