Jerky magic trackpad and keyboard

Hi,

I've had a Mac Mini for about 6 months, and have always used the Apple wireless keyboard and Magic Mouse with it. Everything has been working fine.

Then today I bought a Magic Trackpad as a replacement for the mouse.

After doing a restart on the Mini, everything works fine for a few minutes, and then the cursor movement goes unusably jerky, and the keyboard starts acting weird too, ignoring keystrokes, or repeating them several times. Basically, it becomes impossible to control my Mac.

I have tried turning all the devices (trackpad, keyboard, mouse) off, then turning one on at a time, and it doesn't seem to make any difference, so it doesn't seem to be any single device at fault.

It would appear that the problem is with my Mac or OSX, and has made it I possible to use.

Can anybody please help me?!?