BizTalk XmlException: "'Text' is an invalid XmlNodeType. Line 1, position 1"

If you run into this error during runtime:

A message sent to adapter "WCF-Custom" on send port "SapInvoiceExport" with URI "sap://CLIENT=007;LANG=EN;@a/SAP-SERVER/00?GWSERV=sapgw00&RfcSdkTrace=False&AbapDebug=False" is suspended.
 Error details: System.Xml.XmlException: 'Text' is an invalid XmlNodeType. Line 1, position 1.
   at System.Xml.XmlReader.ReadStartElement(String name)
   at Microsoft.BizTalk.Adapter.Wcf.ComponentModel.IdentityElementSurrogate.ReadXml(XmlReader reader)
   at Microsoft.BizTalk.Adapter.Wcf.ComponentModel.IdentityElementSurrogate.set_ConfigXml(String value)
   at Microsoft.BizTalk.Adapter.Wcf.Config.CustomTLConfig.CreateEndpointAddress()
   at Microsoft.BizTalk.Adapter.Wcf.Runtime.WcfClient`2.InitializeValues(IBaseMessage message)
   at Microsoft.BizTalk.Adapter.Wcf.Runtime.WcfTransmitter`2.GetClientFromCache(String spid, IBaseMessage message)
   at Microsoft.BizTalk.Adapter.Wcf.Runtime.WcfAsyncBatch`2.BatchWorker(List`1 messages)
 MessageId:  {E62F2F57-1727-40A7-81DC-8DF797250933}
 InstanceID: {E59F2C86-D2A7-4A57-B6B0-7C3995676E3A}

... then your WCF Send Port Configuration might have screwed up. You can verify this, if the "Send Port Configuration Wizard" breaks with this error when you press the "Edit Endpoint Identity" button or when you try to export the configuration. The Endpoint Identity itself shows some sort of stars:

 

Solution (July 7, 2014): I imported the binding files with <Password vt="1">pwd<Password><Identity vt="1" />. Since vt contains the type (and format) of the element, it got somehow puzzled. So either use vt="8" or just remove the <Identity> element if you do not need it.

However, the same error can occur also with other mistakes in the Custom props, for example wrong passwords or escaping errors (for example, a non-escaped ">"). Thanks, Christian, for the information!