Virtuoso-t running hard, not talking to kontact

Since an update late last week (I think) I've been seeing a problem with 
virtuoso-t where it's consuming all the CPU in one or more cores (3 right now) 
and for a long time after starting failing to respond to kontact.  On start 
kontact will display the message headers but not the bodies, instead 
displaying a screen saying something to the effect that it's waiting.

Nothing else seems to be affected - the calendar & feeds show normally.

Eventually  virtuoso seems to finish (or stop) what it's doing and all is well. 
To check I restarted the system yesterday and on returning the problem 
returned for some number of hours, only disappearing sometime in the late 
evening.  To double check this morning I logged out and on logging back in the 
excess CPU usage is back and it took kontact about 4 hours to get in and 
display a message.

Here's a chunk of top(1) showing the runtime when I started this message:

19 1318m 923m 7872 S  304 11.6 622:42.66 virtuoso-t          

This is what I'm running:

Qt: 4.8.2
KDE Development Platform: 4.9.1
Kontact: 4.9.1

_______________________________________________
KDE PIM users mailing list
Subscription management: https://mail.kde.org/mailman/listinfo/kdepim-users