Thanks to WinInfo subscriber Noam Rathaus for the tip: Microsoft has posted the sixth hot-fix for Windows NT 4.0 Service Pack 3 to their FTP site. Dubbed the LSA fix, it fixes a bug that occurs when a remote client connects to the Local Security Authority (LSA) over a named pipe and passes an incorrect buffer size (fragment length). This causes an Access Violation error message in Lsass.exe. After this error occurs, you cannot logon locally and the administrative tools that rely on LSA/LSARPC (such as Event Viewer and Server Manager) do not function.
You can download the fix at the Microsoft FTP site