Dave, I have stumbled on a 99 percent solution. In the Wacom Tablet Properties (accessed through the control panel for the Wacom Tablet) the following settings provided help: On the mapping tag with Artrage and Mouse selected for applying settings:
For TOOL: select MouseThis solved the problem except IN THE FIRST INSTANCE of moving the mouse from the left monitor to the right monitor when ArtRage is on the right monitor. In that one case the first click in ArtRage may produce the problem, but all subsequent clicks and drag work correctly as long as I stay INSIDE THE ARTRAGE APPLICATION.
For APPLICATION: select Artrage
Select MAPPING tab
For MODE: select Pen
For SCREEN AREA: select Full.
DO NOT select "Force Proportions" option.
For TABLE AREA: select Full.
Selecting mouse mode rather than pen mode brings back the problem.
Selecting force proportions seems to transfer the initial problem from the mouse to the pen, but with less predictable results.
Meanwhile, the dual monitor configuration causes different intermittent behaviors depending on which of these various settings are selected and when and where clicks are performed as the mouse (or pen) is moved from monitor to monitor and in and out of ArtRage. These may include the direction and distance of cursor displacement, mapping behavior, and tracking speed as the computer attempts to balance different pen and mouse settings between programs while mapping between monitors. It appears the combination of possible settings and monitors can get complex and cause problems.
It seems for now my primary problem is solved with the above settings except the first action of applying a paint tool when moving from one monitor outside of ArtRage to another monitor and into ArtRage, a weird but livable problem.
I suspect others might have different results depending on how ink-services are managed, monitor configurations, Human Interface Devices settings for Vista in the Device Manager (if Vista is the platform), hardware drivers, etc. I've a guess my problem is not a "one size fits all problem", with a "one size fits all solution". But maybe others encountering this problem will benefit from my experience.
I'm interested in any solutions others have found.