Just now, I actually found the problem being addressed on some geek forums
It is specific to the Wacom Bamboo
For now, adding a '--no-wintab' to the shortcut properties fixes the wonkiness, but disables pressure support under Inkscape (and Gimp too)
(
PedroHin Come along & ride on a Flantastic Voyage,
Tue 20 Jan 2009, 1:29,
archived)