Something was wrong with the beta setup I was using (09/15/2008, 23:21:29, 134.579kB, MD5: 813A4C32752E4100A3F0BAE1CEB03811).
I've downloaded a new setup (01/05/2009, 17:24:37, 137.798kB, MD5: 56FD11B2FF1C8F026DD764628725DF1C) and now it seems to be updating ok...
Go figure...