Download the new RouterOS 6.0rc4 release over the torrent network: http://www.mikrotik.com/download/routeros-ALL-6.0rc4.torrent
Otherwise please visit http://www.mikrotik.com/download to pick exact version!
6.0rc4 changelog:
*) dhcp server - added two radius string options (24, 25) for use in custom dhcp options;
*) fixed problem - ppp dial-on-demand did not work, it allways dialed in;
*) fixed problem - password was not saved when adding new user;
*) added feature - show last-logged-in in users list;
*) snmp - fix interface table;
*) dhcp ipv6 - added comment fields;
*) dhcp client ipv6 - add/remove default route or ntp server without renew when settings change;
*) ppp clients - set up dns dynamic-servers instead of static ones;
*) fixed problem - Connect button did not work in wireless scanner;
*) dhcp server - added radius framed route support;
*) fixed problem - MetaROUTERs did not work on PowerPC boards (RB800, RB1000, RB1100);
*) fixed problem - check-for-updates stopped working if it didn't find new updates previously;
*) dhcp ipv6 - added dns option support;
*) gre - support all protocol encapsulation, not just ip and ipv6;