I dowload the Thunderbird from your web site and installed it. After that, I want to lunch it, I recieved above mentioned error. "Thunderbird is already running, but is not responding. To open a new window, you must first close the existing Thunderbird process, or restart your system." Then, I restart my computer, and, open the thunderbird again, but I recieved same message ones more. May be I want to inform you about one thing. One years ago, I used the thunderbird on my computer without any problem. When I want to add a second e-mail account, un fortunately, I did not success. Then, I start to follow my e-mail accounts directly on the internet (Google page, and hotmail mage). And, ı uninstalled the thunderbird from my computer. I want to give you this detail. Can you help me please about, How can I solve this problem ?