Hi all - Telkom did some upgrading on their e-mail environment over the weekend.
This morning I received error messaged when I tried to download emails via Thunderbird.
I tried changing setting after setting and eventually found that it was AVAST antivirus that was causing the problem. I de-activated the mail shield for scanning inbound mail, and the problem disappeared.
I thought that this might be helpful for someone else who might be struggling with the same issue.