I have two email accounts (one is imap, one is pop3) in my older version of Thunderbird. They have both worked normally until last week. The pop3 account continues functioning normally, but now when I select (in Thunderbird) the imap account, the mouse cursor starts showing the hourglass and the bottom status bar reads "loading message" . I've closed and restarted Thunderbird, but this doesn't make any difference. The imap account is stuck on "loading message" and doesn't download anything. I also checked my imap email account on the ISP's website, there is new email there waiting to be downloaded,. What can I do to troubleshoot this?

ps...a few weeks before this problem surfaced, I had all my email (inThunderbird) disappear, so I renamed the prefs.js file and that fixed the problem. My email worked normally after that, until this current problem occured.