Every time I try to promote a W2K server into my W2K domain, after the reboot I get the error message: "LSASS error number 0Xc000003b." The computer can be started in DS repair mode though.
We migrated to W2K half a year ago, but still have our domain in mixed mode. We have created a new root domain with one child domain and this is the domain that now seems to have the problem described above.
I would check to see where the various domain controllers feel where the FSMO roles are located. Creating a new root domain and trying to add a child domain that was actually created first back in, doesn't always work to well. The child domain may still feel like it is the forest root, which could present some problems. Are you having problems with trust relationships as well? Also, the Windows 2000 domain should be placed into native mode as soon as possible. Lastly, if this problem is only occurring on one server, check to see how much memory is on the server, how much of that is available at the time you run dcpromo, and what the registry size limit is. Sometimes low memory conditions can interfere with a proper promotion.