One quick and dirty way to solve the problem is (think twice before you do):
edit index.php of the roundcubemail and find:-
=============
if (empty($_COOKIE))
{
$OUTPUT->show_message("cookiesdisabled", 'warning');
}
==============
and change to
==============
if (empty($_COOKIE) && 1==2 )
{
$OUTPUT->show_message("cookiesdisabled", 'warning');
}
==============
It works for me. Enjoy.
Createch