Recurring email messages in IceDove and I'm feeling deja vu

[Mark Allums <mark@allums.com>]

I am using Icedove, AKA Thunderbird, with an IMAP server.  After 
deleting (or marking for deletion), the messages will reappear in the 
Inbox, or if in the Inbox and marked, they will become unmarked.  This 
happens whether I do it manually or a filter rules "moves" the message 
to a folder.  (The latter occurrence causes one or more copies to be put 
into the intended folder, and the original reappears in the Inbox, 
resulting in at least two copies of the message.)

Is this familiar to anyone?  What's going on?