I can reproduce the problem and solve it. But it's annoying.
The problem :
When I'm in PS, and do cmd+tab (mac OSX). If I come back to my PS, the "Wacom pen" is stuck and doesn't work properly.
If I try to brush something, it makes me only a "point".
Same with healing brush or all the tools that needs to be used by "moving" the cursor.
To solve this problem, I must put my pen on my wacom tablet, and raise it fast.
If I'm fast enough, when I try to brush, it works perfectly...
If I do cmd+tab, same bug again, and solve it by raising it fast again...
So, what's the problem ?
I have done a fresh install of mac OS X, latest PS (all settings to default), latest wacom drivers. Same thing.