This error means that a custom tracing plugin was added to Cassandra to replace standard CQL tracing and that an exception occurred while trying to construct the custom tracing class.
The most likely cause for this error to occur is problems in the code for the custom tracing class. The error is triggered when the custom tracing classed is passed to the FBUtilities.construct method. This method requires that the class it is constructing must have a no-arg or default constructor. If it does not, an exception will occur. Additionally, if the class to construct cannot be found, a configuration exception occurs.
Make sure the class to use for the Custom tracing is in the code base and has the proper constructor.