Since the 2/8 upgrade of Thunderbird the program repeatedly is becoming unresponsive. It can take a long time after starting the program before anything can be done. I have long delays and repeated "Thunderbird is not responding" messages when doing things as simple as clicking on a tab. It eventually responds if I don't force quit. I've been using Thunderbird on Linux for years and have not had this problem before. The unresponsive issue is not a problem with any other program including Firefox. I have zero add-ons loaded. The problem continues when I select "Work Offline". Any advice would be appreciated. Thank you.