if you think there is a corrupted install, installing a fresh download over the existing one is safe. it will use existing profile. for total safety, I suggest doing a backup anyway..

BACKUP

1. ensure thunderbird is not running
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media (or to another folder on disk)

Are all your messages still accessible through webmail at Comcast?

Yes. The situation has changed. My inbox has repopulated, but I can't open an email. When I go to open one, it says "loading message" and nothing loads, for like 15 minutes. The status bar on the bottom says "connecting to" or "connected to" imap.comcast.net, but nothing happens.

However I can open mail that I previously saved go various folders.

Thanks for your reply

David Thank you for your reply. Can you tell me what you mean by "installing a fresh download over the existing one"

Does that mean simply downloading the latest Thunderbird and pressing install without removing or uninstalling the old version?

Right now the Inbox has repopulated so I can see new emails but the problem is I can't open them. It says loading message but it doesn't open. I have numerous time before "network or file access" errors that prevented sending or receiving, which usually resolved itself, but perhaps I do have a corrupted install in that case Rich

yes, install without uninstalling. I presume the old and new are downloaded from thunderbird.net