Accounts switched from Windows Authentication to Project Server au

[ABG]

The process to sync the groups in our Project Server 2003 is scheduled to run
at 3:00am every day. Well, we had an issue where the resources account got
switched from Windows Authentication mode to Project Server Authentication
and no one was able to logon to PWA.

We are trying to figure out how this happened. Here is part of just one of
many errors from the Server's event log:
Component: AD Connector
File: AutoADProcess
Line: -1
Description: .... failed due to error -2147023169-Automation error
The remote procedure call failed and did not execute

Since all of the user accounts authentication mode got switched to Project
Server authentication, the events log showed an error entry for each of the
accounts.

To fix the issue, we manually ran the Enterprise Resource Pool sync process.
All of the accounts were then updated back to the Windows Authentication
mode, then we ran the Groups sync and everything was clear.

Could someone please help me understand how the users' authentication mode
could have been switched from Windows Authentication to Project Server
Authentication? What should we do to prevent this from happening again?

Thanks!