I just purchased a Toshiba Protege M400 laptop/tabletpc around a month ago. It has a 2 Ghz Core Duo processor. The problem I noticed from day one is what I call a 'stuttering mouse pointer'. I can be using it and moving the mouse and then it just stops moving, then jerks and moves to another part of the screen, kind of like a stutter. I am using a external trackball but from what appears it seems it does this from both the trackball as well as the built in touchpad.

Originally I thought this was from the computer being busy and CPU usage near 100% causing it to stutter but I opened task manager and realized often when it does this stuttering CPU usage is at 12-18%. I just can't figure out what's causing this and I haven't used the pc much in tablet mode to konw if it does the same with the tablet pen.

I"m not sure if this is related but starting today my computer has locked up twice where I had a hourglass icon for the mouse pointer and the computer was completely locked up. This didn't happen until today so I honestly think it's not related to this problem

I just don't know if this is a software issue, driver, or a hardware issue. Obviously it's frustrating. I like this tabletpc and don't want to give it up but would return it if this is a common problem or if I have a lemon. Whenever I get a desktop I alwasy build my own computer and install everything. What I don't like is when buying a computer like this there are so many progmams installed I don't need that you can't always uninstall. I am tempted to wipe it out and start over but know then I won't have the tablet pc edition of Windows, OneNote, etc. Any ideas of what I can do to troubleshoot this? Thank you in advance for any help.
P.S. As well, I have all the latest updates, drivers, etc. for this computer.

This is a known behaviour. For tablet pc's there is a special hook for the display which is executed whenever the mouse is moved. The thread for this hook has lower priority then normal, causing the mouse pointer to be jerky. So this occurs on every tablet pc (I have a Toshiba Tecra M4, having the same issue).

Please see http://support.microsoft.com/kb/900475/en-us. Hopefully, Microsoft will release the patch in July or August.

Check this out:

The mouse pointer or pen pointer behavior is irregular in Windows XP Tablet PC Edition 2005

PS. I will wait until the next SP, I have learnt to accept it as a problem after so many months... :-)