This problem is perhaps due to some incompatibility with the latest Wacom drivers( 6.3.14-1 ) which has already been fixed internally. The fix will be available only with the next update of Flash Pro. In the meantime, can you try uninstalling the Wacom drivers and install the previous version of Wacom Drivers(Get it from here: Legacy Drivers | Wacom). Restart your machine and then try using Flash Pro.
Let me know if it still does not fix the problem.