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When I click on a person's name in the chat list, sometimes an invisible chat window opens. I can see the outline of the window, but nothing else. In every session, 3-4 such windows open. I have cleared cache, cookies. I have refreshed browser, restarted everything. Deleted Adblock extension thinking it could be a pop up issue, but nothing has worked. I have the same issue, and every time I need to chat with someone, it can happen at random, so I refresh Gmail and hope that the person I want to talk to at that point, will not end up being such a window. If it is, I refresh again. Sometimes I need to do this 3-4 times to be able to talk to one person.