Found it.
Change line 1444 in program/include/main.inc
from
$input_user = new textfield(array('name' => '_user', 'id' => 'rcmloginuser', 'size' => 30, 'autocomplete' => 'off'));
to
$input_user = new textfield(array('name' => '_user', 'id' => 'rcmloginuser', 'size' => 30, 'autocomplete' => 'on'));
Nico