Keep in mind that a lot of things changed awhile back with Mambo. While some of the old links/sites are still maintained by the people who retained ownership after the dissolve of Miro, the Mambo Foundation has new links that should be used for official releases/news/support.
The official Mambo site is here:
http://www.mambo-foundation.org
The official downloads forge is here:
http://source.mambo-foundation.org/
The official support forum is here:
http://forum.mambo-foundation.org/
The official 3rd party forge is here:
http://mambo-code.org/gf/