MSExchangeIS error

My W2K Xchnge server is a member server with SP3. The application event log is full of warnings about MSExchangeIS, event ID 9543 with error messages such as: Unable to create Public Folder proxy object for “all public folders” in Active Directory.
To go with that I’m also getting a lot of W3SVC warnings in my system event log viewer, with the same error about “The server was unable to logon the windows NT account ‘IUSR-SERVERNAME’ due to the following error: The referenced account is lockedout and may not be logged on to. The data is the error code.”

Any help is appreciated.