Snapshot Error When Adding Article to Transactional Replication

I am trying to add an table articles to my transactional replication setup.   When I do, the snapshot error fails with the following message:

Source: Microsoft.SqlServer.Smo
Target Site: Microsoft.SqlServer.Management.Smo.SqlSmoObject GetSmoObject(Microsoft.SqlServer.Management.Sdk.Sfc.Urn)
Message: Attempt to retrieve data for object failed for Server '<servername>'.
Stack:    at Microsoft.SqlServer.Management.Smo.Server.GetSmoObject(Urn urn)
   at Microsoft.SqlServer.Replication.Snapshot.SmoScriptingManager.BuildSmoObjectArrayAndUrnLookupTable(IDictionary& dictUrnKeyArticleScriptingBundles)
   at Microsoft.SqlServer.Replication.Snapshot.SmoScriptingManager.DoScripting()
   at Microsoft.SqlServer.Replication.Snapshot.SqlServerSnapshotProvider.DoScripting()
   at Microsoft.SqlServer.Replication.Snapshot.SqlServerSnapshotProvider.GenerateSnapshot()
   at Microsoft.SqlServer.Replication.SnapshotGenerationAgent.InternalRun()
   at Microsoft.SqlServer.Replication.AgentCore.Run() (Source: Microsoft.SqlServer.Smo, Error number: 0)
Get help: http://help/0
Source: Microsoft.SqlServer.Smo
Target Site: Microsoft.SqlServer.Management.Smo.ObjectKeyBase CreateKeyFromUrn(Microsoft.SqlServer.Management.Sdk.Sfc.Urn)
Message: The input Urn must specify Name at level UserDefinedFunction.
Stack:    at Microsoft.SqlServer.Management.Smo.SchemaCollectionBase.CreateKeyFromUrn(Urn urn)
   at Microsoft.SqlServer.Management.Smo.Server.GetSmoObjectRec(Urn urn)
   at Microsoft.SqlServer.Management.Smo.Server.GetSmoObject(Urn urn) (Source: Microsoft.SqlServer.Smo, Error number: 0)
Get help: http://help/0

Specifics:

• Transactional replication:  Both Immediate Sync and Allow Anonymous are set to 0.
• Publisher and Distributer are same server:  SQL Server Standard 2008 R2 (10.50.4000.0) on Windows 2008 R2 SP1
• If I add even one table article (doesn't matter, I've tried different ones), I get the error above when I run the snapshot agent.
• If I remove the table just added and rerun the snapshot agent, it succeeds with the message "A snapshot was not generated because no subscriptions needed initialization", so at least I don't have to reinitialize (thank goodness!).

Any ideas as to what might be causing this, and how I can add articles to my existing publication?

Thanks in advance for your help.