[canghel]

I found the culprit:

After the migration, the LDAP AU got messed up. Of course, since the the LDAP groups I have were relying on the AU those were messed up too.

I fixed the LDAP AU and the LDAP groups and I was able to log on (but with no access to resources).

After a lot of pain I realized that the cannonical name in the LDAP groups had a "CN" instead of an "OU". (And if was hard to find since the name was longer than the entry box, so not all of it was visible...)