Sharing between IMAP and IMAP-SSL seems broken

If I have an IMAP folder open in a buffer, and try to open the same folder via IMAP-SSL, then VM seems to reuse the same folder buffer for opening the folder.

However, something goes wrong, and VM is actually opening an IMAP connection, which may or may not work. It gives an error message

make client process failed: connection timed out, :name, IMAP, :buffer, MAIL mailhost.c 17:45:49, :host, mailhost.cs.bham.ac.uk, :service, 143, :nowait, nil
apply: Could not connect to the IMAP server

The IMAP connection buffer shows

Starting IMAP session Sun Jan 26 17:45:49 2014

-- connecting to mailhost.cs.bham.ac.uk:143