I solved the issue. It was indeed a path issue. If classes depend on other .jar then those need to be added to the javaclasspath as well.
Following the quickfix installation guide the following 4 jar files need to be in the path:
quickfixj-all.jar(includes core and message JARs)
1) The Banzai example is running correctly on my system.
2) The javaclasspath is set correct.
I'm successful calling (and creating the output objects in Matlab) other classes from the same quickfixj-all jar files.
The error is telling you it can not find the SocketInitiator method. This error is likely due to one of these reasons:
1) the required library is not on the javaclasspath
2) a mis-match in required java libraries
When you download and install quickfix/j, run the banzai example outside of MATLAB to make sure your system has all of the required java libraries. If it runs correctly, then the problem is in the importing/classpath.txt reference to the required java libraries, which you can fix by importing the libraries from the same directory as the installation of quikcfix/j.