When running Full screen(1600x1200), clicking on a button in
the toolbar, the button will often gets stuck (i.e. the button does not receive any release events).

It can be made to occur more often by pushing on the button, dragging
the cursor away and then back onto the button.

I've installed an event filter into the application and it appears that
tablet release and click events are being fired but mouse clicks are not.

I have a wacom Intuos3 tablet.

The application that we seem to have the problem with is one where there is heavy calculations that causes the CPU usage to max out.
I believe the problem has something to do with the heavy calculation as a using smaller window for rendering, or less triangles makes the problem less obvious / disappear.

I tested it with a QTextEdit as opposed to our 3d graphical widget, and was unable to replicate the problem.

This test app replicates a problem we were seeing in our 3D application
where tablet clicks were not working when the scene we were rendering became very heavy. Light scenes do not display this problem.