Thunderbird unresponsive

Hi, Several times a day, at least three or four, Thunderbird becomes unresponsive. I just get the little rotating circle and nothing else. It will go this for as much as three or four minutes. I have reloaded Thunderbird twice with no improvement. It happens on all three of my computers running Thunderbird. My mail comes through Google mail and I have two accounts, one through the University and a second private one. They both respond the same way. My computers are PC's. I hope you can help me as I much prefer Thunderbird over the browser email client for google mail. My email is dand@umn.edu Thanks in advance Dan Dahlberg