Unable to open mailbox

[Patrick Welche <prlw1@xxxxxxxxx>]

Using a very recent -HEAD mutt, and a cyrus server, I suddenly can't open a
very large INBOX. Essentially:

[2009-11-10 11:19:13] 4< * 233696 FETCH (FLAGS (\Seen) UID 733819 
INTERNALDATE "
5-Nov-2009 10:16:07 +0000" RFC822.SIZE 7428 BODY[HEADER.FIELDS (DATE FROM 
SUBJE CT TO CC MESSAGE-ID REFERENCES CONTENT-TYPE CONTENT-DESCRIPTION 
IN-REPLY-TO REPL Y-TO LINES LIST-POST X-LABEL)] {708} [2009-11-10 11:19:13] 
Handling FETCH [2009-11-10 11:19:13] FETCH response ignored for this 
message [2009-11-10 11:19:13] imap_read_literal: reading 708 bytes 
[2009-11-10 11:19:13] Connection to localhost closed [2009-11-10 11:19:15] 
imap_read_literal: error during read, 319 bytes read [2009-11-10 11:19:15] 
Error opening mailbox

733819. looks like a well formed message - I suspect that

List-Subscribe: <http url on one line>,
      <tab, and then mailto url on next>

is allowed?

So have you any suggestion on where to look for more of a clue as to what 
happened? Is the error message really saying "look at the server as it 
terminated the connection"?

mutt terminates cleanly, so it's probably not because the inbox has over 
230,000 messages in it and is overflowing somewhere?

Cheers,

Patrick