When messaging users, the course short name in the breadcrumb trail is not hyperlinked (at least in Firefox 2). The reason for this is a simple </A> instead of </a>. I just thought I'd report it because it's been there for quite some time. To fix:

Modify (around) line 63 where the print_header() function is and change this:

print_header($strtitle,$strtitle,"<a href=\"$CFG->wwwroot/course/view.php?id=$course->id\">$course->shortname</A> > <a href=\"index.php?id=$course>id\">".get_string("participants")."</a> -> ".$strtitle,$formstart);

to this:

print_header($strtitle,$strtitle,"<a href=\"$CFG->wwwroot/course/view.php?id=$course->id\">$course->shortname</a> > <a href=\"index.php?id=$course>id\">".get_string("participants")."</a> -> ".$strtitle,$formstart);