Windows 7 64-bit
Not sure if it's ever worked, Blender built Sept 13 2014, unknown hash
Short description of error
I have a modal script where the value of a custom property is driven by mouse location. Script runs and completes without issue, but the value of the custom property doesn't update until I mouse over the custom property GUI. Additionally the custom property drives a shape key value. The shape key value doesn't update even after forcing the update in the custom properties panel, and doesn't update until clicking the value slider and canceling with right click.
As a side note, if updating the custom property manually in the GUI, everything updates as expected. It seems to only be a problem when driven by the script.
Exact steps for others to reproduce the error
Open the file, click run script, move the mouse to the right, and left click to end to modal operation. The foo value in the GUI isn't updated until running the mouse over the foo slider. Then, to update the shape key, switch to the shape key menu and click/unclick the shape key value slider.