One button upload component shows the underlying file input

I am using the 1 click upload component.
recently it started to misbehave.
When I would click on the upload button, select the file, press ok, the native file input would appear in the page. (See attached screenshot)
Moreover if this component is in a window, if I close the window VAADIN complains it is desynchronized and that I have to sync the app by clicking the red label at the top of the page.
The client keeps on contacting the server sending a payload like : b4f3aa90-1c42-4dd8-8b50-15fe800268021PID135pollForStarti
it seems it doesn’t happen in simple setups.
I have the main window plus an additional window on top, and the upload component is in the top most window.
Any clues ?
I am testing with vaadin 6.6.1, but it was the same with 6.6.6 and 6.7.0
it happen mostly on chrome, then ie, and rarely on firefox.