Same thing has been happening to me, I have to reboot every time it happens to solve the problem, but then it comes back. For instance, when uploading to WC, when I click the button to upload the screenshot or file, nothing happens. When right clicking on an image and then click "Save Image As", nothing happens, no dialog window, and again I have to again reboot.
The problem does not occur in IE, just Chrome, and the latest version is what I have installed.