[zenon]

If this were not an intermittent problem I would try various ways of
unlocking the document. But it happens every few comments I insert.
I get the usual "this modification is not allowed because the document
is locked" Nothing else is locked and even the comments field is not
locked most of the time. But as I go on typing a comment I find that
the last few words were not entered because of this lock glitch. The
way out of this is to click a space in the comments box and then it
usually lets me insert at that insertion point. (By the way, the same
is true and more reliable of deletions -- if I select a string of text
and hit the delete key I usually get the "this modification ...."
message.)