KMail locks up

Ok. I've mentioned this problem before, but I can't find that thread right 
now (several weeks ago) so I'll start a new thread.

Basically, what happens is that I will come home from work, start KMail 
(Note: I'm NOT starting the full KDE-PIM suite, just KMail and the 
associated apps, such as address book, etc.) and after a few minutes, KMail 
will be come unresponsive. sometimes, it's after I've started a message, 
but not always.

In every case, if I use kill -9 on all the kmail-related PIDs, and stop 
Akonadi, and restart KMail, I'm fine, but I'd really rather not have to go 
that route.

I do wonder if maybe when I shut down KMail in my VNC session, it's leaving 
something running and that's confusing things? Any suggestions as to what 
to look for?