If you have archiving enabled, check the size of the archive if this
is a high traffic list.
I ran into this problem a month or so ago, with one of our internal
lists. It was taking so long to add the message to the archives
that the qrunner process could never finish processing the messages
If your list is being archived, you might want to see if the archive
has grown excessively large.
I ran into this exact problem with one of my lists a few months ago,
but no one has as yet been able to answer yes or no to the questions
I posed back then...mostly regarding the impact of list
