Right. It only does it when working on the Wacom using SBP. My other monitor is running too (clone setting) and it works fine. Also, when I try to select a different tool / color / etc. it doesn't show all the options . . . I have to remember where they are and "blindly" drag the pen to select them. I haven't used it in a while since it's been a pain.
Try reinstalling the wacom driver and recalibrating the stylus. I've seen offset problems on Vista which were fixed when I reinstalled the driver. The violent crosshair shifting I've not seen before. What graphics card are you using, are you using a dual monitor? In some dual screen modes there can be a potential for cursor magneting that I've seen in the past.
i reinstalled the driver and before calibrating the pen everything works okay . . . just a little misaligned. it's when i calibrate the pen that i run into the crosshair shaking. after that happens i just delete the user preferences and deal with the slight misalignment. if i change my seating position and point of view it lines up okay . . . kinda a stupid work-around though. i have a NVIDIA Quadro FX 3400/4400 graphics card.