You can reinstall the sites as standalones and see if that will let you login but you may need to clear the usergroups table first before reinstalling.
Actually just for clarification Mambo is still being developed Home - The Mambo Foundation
Why would you sites be broken if you are still using mambo unless you switched to Joomla which we dont support?
Basically mambo is still around and joomla is an offshoot. Their was a developer war over at mambo and the teams split and both products are being developed in separate directions. at least thats my understanding.