I have the same issue with my hp TC1100 tabletPC.
A tabletPC uses a WACOM tablet built-in to the screen. A pen held over the screen at any point moves the mouse cursor to that point (in windows).
In DosBox 0.72 instead of the cursor following the pen, it jumps crazily to the edges of the screen. I noticed in one case I could control it loosely by only moving the pen in the upper right quarter - as if the entire screen coordinates were mapped to the upper right 320x240. However, it is very jittery and unplayable!
I attempted tweaking the fullscreen resolution from original to my computer's native resolution of 1024x768, but it had not effect on the mouse tracking.
It must have something to do with how the mouse is tracked - traditional mice only provide a change in position to the PC. However, the tablet input moves the mouse cursor to the position the pen hits the screen an absolute coordinate instead of a change in coordinate. I am posting this in the development forum as well to see if I can get some help looking at the DosBox source code for the mouse interpretation.
EDIT: I found a thread from last year with some development info on trying to fix the problem here: Wacom Tablet+Dosbox+Autodesk Animator Pro