What happens if you right click the desktop and select the refresh or if you selct show desktop by clicking the far right of the taskbar. I have on the quick launch, show desktop and switch between windows. Sometimes when something gets stuck on the screen, one of the options I listed will dispose of it.
I'm not sure if show desktop will dispose it, but I'll try when it happens again.
Does it just happen in Chrome? Firefox once did this for me way back when I used to be actively involved in theme customization. Context menus would stick to the screen when the expected result was that the menu is destroyed when said menu has lost focus. In my case, it turned out to be some wrong values in the .css code.
It seems to be able to happen anywhere, just that when it decided to "stick" tabs, the first tab I click is in Chrome.
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