Getting Error Accessing Certain IBM Connections Blog using IBM Social Business Toolkit SDK via Java: SBT context is not initialized for the request

I have a Java agent in a Domino database to read blog posts from an on-premisis IBM Connections 4.5 installation using the Social Business Tooklit SKD. The java agent is able to access several test blogs and retrieve the list of blog posts, but other blogs in the same environment are generating the following error:

HTTP JVM: com.ibm.sbt.services.client.ClientServicesException: SBT context is not initialized for the request

The error is being thrown on the following line:

Blog bo = blogService.getBlog(bRef.getId());

All of the blogs are accessible directly via a browser, and the Java agent can access some of the blogs, but consistently throws this error when attempting to get a handle to others. I have been unable to identify any differences in the setup or access restrictions of the blogs. Does anybody have any ideas on where to look?