Finally got it working, everything was related to a block in the mysql (the solution is to perform a mysqladmin -flush-hosts -p.
What made me sick for a while was that the connection failing was from the slave to the master, and I was performing the mysqladmin on the slave, but the debug info on the slave only stated the error without indicating where it was trying to connect. And I wasn't able to figure it until I modified server.php and added an echo with the DBHost, DBUser and DBPass. After I performed it on the master server everything started working fine.
Regards, happy new year.