I just got a Trust tablet. As far as I can tell, it is set up correctly.. but the cursor keeps shaking rapidly whenever I use the pen.

This makes it quite difficult to draw free hand with the tablet... thus making it pretty much useless..

Is there anyway i can prevent this?

I had the same problem, have had the tb-4200 for a while now and had no problems with it until I upgraded to vista. The tablet worked fine, except the pen pressure didn't work in photoshop, the drivers fixed this but made the pen unusable due too flickering.

I eventually managed to fix it, I believe the problem is caused by a conflict with the vistas inbuilt tablet support and the tb-4200 drivers. I managed to fix it by stopping and disabling the "Tablet PC input services" in vista, to do this click start, type in "services" and run that program, find the "Tablet PC input services" service in the list and double click it, then click stop and change the start up type to "Disabled" or "Manual" note, disabled will stop it from ever running (unless you set it to something else) manual will only stop windows from auto loading it when vista starts (it might still load it if you use the tablet, but I am not sure). I just set it to disabled to stop it running altogether and the tablet works well.

NOTE: Disabling services can cause applications to fail to load or work effectively if you disable a service that they relay on. You can turn them back on the same way you turned them off if a problem arises, do at your own risk.

I got the exact same problem and google brought me here.
I tryed your solution but it didn't work. When I disable the service, the pen simply doesnt respond anymore. Meaning the tablet really needs the service in order to work. I also got a TB4200 and contacted Trust about it but they haven't got a solution other than 'download latest driver' (already got that).
It's like the pen is always touching the board. The same effect as using your mouse while continously holding down the leftmouse button. It's quite annoying. If anyone has a solution, ill be happy to hear about it!