PDC will not run with any BDC.

Here's an Interesting one. I have a Network with over 70 Workstations and 7 servers. Everything works fine if I have no BDC's up and running. The PDC will run everything without error. But if I turn on either of my 2 BDC's then users get kicked out of the network, Authentication becomes hit and miss and the SAM for the BDC's become corrupt. Up to date 3 different Administrators have rebuilt(or built) 3 different servers as BDC. It seems to work for about 2 or 3 days and then the BDC gets corrupted. The SAM for the PDC appears to be fine and I don't want to reload my PDC from scratch and lose my user data or accounts. Promoting a BDC and taking the PDC off to reload seems the only option but the fear is that if something is corrupt then allI'm doing is transferring the problem and not getting rid of it. Any Suggestions???