For two weeks now, I've been receiving the following error message whenever I open Thunderbird: "Unable to open folder inbox on xxxxx@earthlink.net because it is in use by some other operation. Please wait for that operation to finish and then select the folder again." I have no idea what operation it may be referring to. I still get this message if Thunderbird is the first thing I open when I turn the computer on. I can see my email on Earthlink, but it is a very awkward program, with no way to mark email important, and other problems. For years I've had messages automatically downloaded to Thunderbird, and this problem never happened before. Other details: I am able to send messages on Thunderbird. I am using an older computer with Windows 10. Thank you! Paul Geidel