Hi,
RichText box can be binded to only main datasource nodes for editing.
If your webservice connection is a main dataconnection then you can bind your strings to a richtextbox. The reason for this is,
When you add a richtext box to UI then one reference of it is stored in manifest.xsf, This is for enabling richtext features. Most of the time secondary datasource references are not stored in manifest.xsf file.
So if you want to edit your fields with richtextbox then they need to be main datasource fields.
Agni
InfoPath Dev India