Description of Problem: I have an intermittent but frequent problem where
when I select an HTML email message, Evolution will display it in the
preview pane, but then nothing I do can change the content of the preview
pane.  The status bar will say "Formatting message (...)" until I restart.
This happens very frequently with "headline" emails from the New York
Times, but other (complicated) HTML mail as well.  Might well be an
underlying gtkhtml bug, but Evolution should  be able to interrupt whatever
gtkhtml is doing when rendering messages.

Steps to reproduce the problem:
1. Copy the attached message into a mailbox
2. Start Evo and select message
3. Change folder/change display/select different message or hit "Cancel" button

Actual Results: The message stays in the preview pane.

Expected Results: New message/folder opens, display changes to "source", or
when I press "Cancel", the "FOrmatting message (...)" in the status bar
should go away.

How often does this happen?  Often.