Microsoft Knowledge Base Article 810977 contains the following summary:

When you use Event Viewer to view the system log in a Windows 2000 Server-based domain controller, you may find event 5722 logged. This problem may occur in either of two scenarios:

When a computer updates its computer account password with a domain controller
When a computer is joined to a domain with a name that already exists
This article describes how to differentiate the two scenarios and how to resolve the problem.