I have this working now I think on the manage posts function as well. I changed:
if (strstr($_SERVER['PHP_SELF'], 'post-new.php') ||
strstr($_SERVER['PHP_SELF'], 'page-new.php'))
to:
if (strstr($_SERVER['PHP_SELF'], 'post-new.php') ||
strstr($_SERVER['PHP_SELF'], 'post.php') ||
strstr($_SERVER['PHP_SELF'], 'page-new.php'))
and it seems to work correctly. BUT, I just did this quickly from work and have only done very limited testing.
So far so good however.