qt message fail

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I have a large ROS package including python and C++ nodes and also a C++ GUI in QT. The QT node interacts with other ROS nodes via service calls and that works great. Ros::spinOnce is being called in a loop in a separate QThread and I've confirmed with log statements that that loop is running. However when I try to instantiate a msg publisher on the same node handle as used successfully for the service client, the following happens:

1) ROS logs and rqt shows that the publisher is properly advertised 2) publisher.publish() statments result in no output (either to console or to ROS logs).

My non-QT C++ nodes publish and receive messages without difficulty in the standard manner.

Any ideas??