When compose_new_win pref is set to 1, some users
can't compose any new mail (reply, forward, ...)
I've worked on the bug and here is what i've found :
error : "comp_in_new is not defined" ...
so i looked into functions/page_header.php and found
that the js function is defined only if
onclick="comp_in_new()"> link is displayed only if
$compose_new_win == '1'
and both case are not equivalent. So there is a bug
this might not be the only place where it can occur but
a grep sould give it.