[SOLVED] Stage Mouse Watcher says "nan"

[dbini]

Hi folks, I'm building a live drawing patch that makes use of a Wacom drawing tablet. I've got Stage Mouse Watcher rigged up to a Live Drawing actor and it works really nicely.
but, during testing today, the Horiz. Pos output of the Stage Mouse Watcher suddenly became 'nan' - so the horiz. pos. of the Live Drawing also became nan.
I had to replace the Stage Mouse Watcher actor with a fresh one before I could get it to function again.
Any ideas why this happened and how I might be able to prevent it from happening again?

[dbini]

i can see that the Limit Horiz input got switched to zero somehow, which would explain why the actor ceased to function, but not the 'nan' 
I think i need to disable the click buttons on the Wacom pen - its too easy to disrupt the patch.

Is there a better way to get data from the Wacom? its not showing up as a HID.

[dbini]

i just discovered that 'nan' generally means 'Not a Number'