[ActiveDir] 2 AD DCs but only one accepting authentication

[EN]

I have 2 AD DCs, and when the first created DC of the domain fails, the 2nd DC doesn't accept logons. I'm running mixed mode the GC only being on the first DC shouldn't matter right?  Has anyone else encounted this type of problem?  When I promoted the 2nd server to a DC, everything went smoothly, sysvol and netlogon shares were created properly.      Each DC has a DNS server as well, with the 1st DC having an AD Integrated DNS, while the 2nd has a Primary DNS, and yet another stand alone has a secondary dns.  All the dns records "seem" right, in that the svr records are showing up in each DNS server.     Any ideas on what too look for to maybe solve this problem?   thanks   Ernesto