AD Setup

Hi everyone,

I have an abnormal behavior with my AD setup. i have 2 ADs in the head office(one running Server 2003 R2, another Server 2008 R2 SP1) and another AD in a branch office running Server 2008 R2 SP1. ALL DCs have GC and the FSMO roles are on one DC which is the 2003 R2 at the head office, when the branch network goes off all users are not able to authenticate and when i restart the primary AD(2003 R2) it takes too long to come-up, it keeps displaying "preparing your network connections" for more than 30 mins then once its up even the mails and exchange server in the head office do not work. I thought the primary AD should always authenticate as long as its up?

Meshack